Improve -win7-windows-msvc documentation

Author: roblabla

src/doc/rustc/src/platform-support/win7-windows-msvc.md

@@ -10,13 +10,13 @@ Windows targets continuing support of windows7.
 
 ## Requirements
 
-This target supports full the entirety of std. This is automatically tested
-every night on private infrastructure. Host tools may also work, though those
-are not currently tested.
+This target supports all of core, alloc, std and test. This is automatically
+tested every night on private infrastructure hosted by the maintainer. Host
+tools may also work, though those are not currently tested.
 
 Those targets follow Windows calling convention for extern "C".
 
-Like with any other Windows target created binaries are in PE format.
+Like any other Windows target, the created binaries are in PE format.
 
 ## Building the target
 
@@ -30,15 +30,51 @@ target = [ "x86_64-win7-windows-msvc" ]
 
 ## Building Rust programs
 
-Rust does not yet ship pre-compiled artifacts for this target. To compile for
-this target, you will either need to build Rust with the target enabled (see
-"Building the target" above), or build your own copy of `core` by using
-`build-std` or similar.
+Rust does not ship pre-compiled artifacts for this target. To compile for this
+target, you will either need to build Rust with the target enabled (see
+"Building the target" above), or build your own copy by using `build-std` or
+similar.
 
 ## Testing
 
-Created binaries work fine on Windows or Wine using native hardware.
+Created binaries work fine on Windows or Wine using native hardware. Remote
+testing is possible using the `remote-test-server` described [here](https://rustc-dev-guide.rust-lang.org/tests/running.html#running-tests-on-a-remote-machine).
 
 ## Cross-compilation toolchains and C code
 
 Compatible C code can be built with either MSVC's `cl.exe` or LLVM's clang-cl.
+
+Cross-compilation is possible using clang-cl/lld-link. It also requires the
+Windows SDK, which can be acquired using [`xwin`](https://github.com/Jake-Shadle/xwin).
+
+- Install `clang-cl` and `lld-link` on your machine, and make sure they are in
+  your $PATH.
+- Install `xwin`: `cargo install xwin`
+- Use `xwin` to install the Windows SDK: `xwin splat --output winsdk`
+- Create an `xwin-lld-link` script with the following content:
+
+  ```bash
+  #!/usr/bin/env bash
+  set -e
+  XWIN=/path/to/winsdk
+  lld-link "$@" /libpath:$XWIN/crt/lib/x86_64 /libpath:$XWIN/sdk/lib/um/x86_64 /libpath:$XWIN/sdk/lib/ucrt/x86_64
+  ```
+
+- Create an `xwin-clang-cl` script with the following content:
+
+  ```bash
+  #!/usr/bin/env bash
+  set -e
+  XWIN=/path/to/winsdk
+  clang-cl /imsvc "$XWIN/crt/include" /imsvc "$XWIN/sdk/include/ucrt" /imsvc "$XWIN/sdk/include/um" /imsvc "$XWIN/sdk/include/shared" --target="x86_64-pc-windows-msvc" "$@"
+  ```
+
+- In your config.toml, add the following lines:
+
+  ```toml
+  [target.x86_64-win7-windows-msvc]
+  linker = "path/to/xwin-lld-link"
+  cc = "path/to/xwin-clang-cl"
+  ```
+
+You should now be able to cross-compile the Rust std, and any rust program.