Unrolled build for rust-lang#126916

Rollup merge of rust-lang#126916 - ferrocene:hoverbear/riscv64gc-gnu-specify-linker, r=Kobzol

Specify target specific linker for `riscv64gc-gnu` job

In rust-lang#125669 I updated the `riscv64gc-gnu` job to be more in line with other jobs, like the `armhf-gnu` one.

I missed something important, though! Since the `riscv64gc-unknown-linux-gnu` builds go through a cross compiler, invoking `cc` is not correct! That would invoke the `x86_64-unknown-linux-gnu` linker, instead of the `riscv64gc-unknown-linux-gnu` linker.

While developing rust-lang#125669 I assumed this line would have been sufficient, however it was not:

https://github.com/rust-lang/rust/blob/553a69030e5a086eb3841d020db8c9c463948c72/src/ci/docker/host-x86_64/disabled/riscv64gc-gnu/Dockerfile#L27-L28

Unfortunately, without the linker set, `cc` is invoked, and the following linker error occurs:

<details>

<summary>Long output</summary>

```
2024-06-21T14:37:54.4786899Z === HAYSTACK ===
2024-06-21T14:37:54.4787240Z error: linking with `cc` failed: exit status: 1
2024-06-21T14:37:54.4787589Z   |
2024-06-21T14:37:54.4806781Z   = note: LC_ALL="C" PATH="/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/bin:/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/bin:/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" VSLANG="1033" "cc" "/tmp/rustc7Ju6va/symbols.o" "inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o" "inaccessible/tmp/program.dv9uftjrq86w5xa7l2eo7g9l7.rcgu.o" "-Wl,--as-needed" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/run-make/inaccessible-temp-dir/inaccessible-temp-dir/rmake_out" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib" "-Wl,-Bstatic" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libstd-bb9ed017b7d70437.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libpanic_unwind-5b34ef68c22a7b9b.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libobject-4b9224407e296f51.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libmemchr-1eaaa8d74bbe0b36.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libaddr2line-b34292f7086867e9.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libgimli-1927540c5dff6690.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/librustc_demangle-ab493befe3742702.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libstd_detect-41195694489636c4.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libhashbrown-6905da49c8a1542a.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/librustc_std_workspace_alloc-bbc6290f03f92349.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libminiz_oxide-7a4683d4a82cf47c.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libadler-071583516cdbce90.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libunwind-d84b176d2f4c1334.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libcfg_if-92b7de0160f87442.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/liblibc-cff1533ea7c26263.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/liballoc-49e374c13f9e6132.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/librustc_std_workspace_core-9389dcc15b2f7f7b.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libcore-46f0fa14905fdc5c.rlib" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib/libcompiler_builtins-20e1af401f90cd1c.rlib" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-Wl,--eh-frame-hdr" "-Wl,-z,noexecstack" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/riscv64gc-unknown-linux-gnu/lib" "-o" "program" "-Wl,--gc-sections" "-pie" "-Wl,-z,relro,-z,now" "-nodefaultlibs"
2024-06-21T14:37:54.4823900Z   = note: /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4825032Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4826130Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4827200Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4828279Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4829365Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4830474Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4831554Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4833002Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4834116Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: Relocations in generic ELF (EM: 243)
2024-06-21T14:37:54.4835237Z           /usr/bin/ld: inaccessible/tmp/program.program.45572bc5f2b14090-cgu.0.rcgu.o: error adding symbols: file in wrong format
2024-06-21T14:37:54.4835971Z           collect2: error: ld returned 1 exit status
2024-06-21T14:37:54.4836449Z
2024-06-21T14:37:54.4836584Z
2024-06-21T14:37:54.4836744Z error: aborting due to 1 previous error
2024-06-21T14:37:54.4836983Z
2024-06-21T14:37:54.4836990Z
2024-06-21T14:37:54.4837083Z === NEEDLE ===
2024-06-21T14:37:54.4837518Z failed to find or create the directory specified by `--temps-dir`
2024-06-21T14:37:54.4838250Z thread 'main' panicked at /checkout/tests/run-make/inaccessible-temp-dir/rmake.rs:35:14:
2024-06-21T14:37:54.4838801Z needle was not found in haystack
2024-06-21T14:37:54.4839270Z note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
2024-06-21T14:37:54.4840125Z thread 'main' panicked at /checkout/tests/run-make/inaccessible-temp-dir/rmake.rs:27:5:
2024-06-21T14:37:54.4840759Z called `Result::unwrap()` on an `Err` value: Any { .. }
2024-06-21T14:37:54.4841194Z ------------------------------------------
```

</details>

By setting `--set target.riscv64gc-unknown-linux-gnu.linker=riscv64-linux-gnu-gcc` the correct linker is invoked.

## Testing

> [!NOTE]
> `riscv64gc-unknown-linux-gnu` is a [**Tier 2 with Host Tools** platform](https://doc.rust-lang.org/beta/rustc/platform-support.html), all tests may not necessarily pass! This change should only make fix existing broken tests (like `inaccessible-temp-dir`) while introducing no new breakage.

You can test out the job locally:

```sh
mv src/ci/docker/host-x86_64/disabled/riscv64gc-gnu src/ci/docker/host-x86_64/riscv64gc-gnu
DEPLOY=1 ./src/ci/docker/run.sh riscv64gc-gnu
```

src/ci/docker/host-x86_64/disabled/riscv64gc-gnu/Dockerfile

@@ -91,7 +91,9 @@ RUN sh /scripts/sccache.sh
 # Avoid "fatal: detected dubious ownership in repository at '/checkout'" error
 RUN git config --global --add safe.directory /checkout
 
-ENV RUST_CONFIGURE_ARGS --qemu-riscv64-rootfs=/tmp/rootfs
+ENV RUST_CONFIGURE_ARGS \
+    --qemu-riscv64-rootfs=/tmp/rootfs \
+    --set target.riscv64gc-unknown-linux-gnu.linker=riscv64-linux-gnu-gcc
 ENV SCRIPT python3 ../x.py --stage 2 test --host='' --target riscv64gc-unknown-linux-gnu
 
 ENV NO_CHANGE_USER=1