Directly link more target docs

Some platforms were not linked from platform-support.md

This fixes that, but errs towards extremely conservative,
only directly linking platform docs if the docs actively
mention the target, as otherwise I do not necessarily
know if there was a reason for the omission.

Author: workingjubilee

src/doc/rustc/src/platform-support.md

@@ -101,7 +101,7 @@ target | notes
 `x86_64-unknown-freebsd` | 64-bit FreeBSD
 `x86_64-unknown-illumos` | illumos
 `x86_64-unknown-linux-musl` | 64-bit Linux with MUSL
-`x86_64-unknown-netbsd` | NetBSD/amd64
+[`x86_64-unknown-netbsd`](platform-support/netbsd.md) | NetBSD/amd64
 
 ## Tier 2
 
@@ -128,7 +128,7 @@ target | std | notes
 `aarch64-apple-ios` | ✓ | ARM64 iOS
 [`aarch64-apple-ios-sim`](platform-support/aarch64-apple-ios-sim.md) | ✓ | Apple iOS Simulator on ARM64
 `aarch64-fuchsia` | ✓ | Alias for `aarch64-unknown-fuchsia`
-`aarch64-unknown-fuchsia` | ✓ | ARM64 Fuchsia
+[`aarch64-unknown-fuchsia`](platform-support/fuchsia.md) | ✓ | ARM64 Fuchsia
 [`aarch64-linux-android`](platform-support/android.md) | ✓ | ARM64 Android
 `aarch64-unknown-none-softfloat` | * | Bare ARM64, softfloat
 `aarch64-unknown-none` | * | Bare ARM64, hardfloat
@@ -159,7 +159,7 @@ target | std | notes
 `mips64-unknown-linux-muslabi64` | ✓ | MIPS64 Linux, n64 ABI, MUSL
 `mips64el-unknown-linux-muslabi64` | ✓ | MIPS64 (LE) Linux, n64 ABI, MUSL
 `mipsel-unknown-linux-musl` | ✓ | MIPS (LE) Linux with MUSL
-`nvptx64-nvidia-cuda` | * | --emit=asm generates PTX code that [runs on NVIDIA GPUs]
+[`nvptx64-nvidia-cuda`](platform-support/nvptx64-nvidia-cuda.md) | * | --emit=asm generates PTX code that [runs on NVIDIA GPUs]
 `riscv32i-unknown-none-elf` | * | Bare RISC-V (RV32I ISA)
 `riscv32imac-unknown-none-elf` | * | Bare RISC-V (RV32IMAC ISA)
 `riscv32imc-unknown-none-elf` | * | Bare RISC-V (RV32IMC ISA)
@@ -182,7 +182,7 @@ target | std | notes
 `x86_64-apple-ios` | ✓ | 64-bit x86 iOS
 [`x86_64-fortanix-unknown-sgx`](platform-support/x86_64-fortanix-unknown-sgx.md) | ✓ | [Fortanix ABI] for 64-bit Intel SGX
 `x86_64-fuchsia` | ✓ | Alias for `x86_64-unknown-fuchsia`
-`x86_64-unknown-fuchsia` | ✓ | 64-bit Fuchsia
+[`x86_64-unknown-fuchsia`](platform-support/fuchsia.md) | ✓ | 64-bit x86 Fuchsia
 [`x86_64-linux-android`](platform-support/android.md) | ✓ | 64-bit x86 Android
 `x86_64-pc-solaris` | ✓ | 64-bit Solaris 10/11, illumos
 `x86_64-unknown-linux-gnux32` | ✓ | 64-bit Linux (x32 ABI) (kernel 4.15, glibc 2.27)
@@ -332,6 +332,6 @@ target | std | host | notes
 `x86_64-uwp-windows-gnu` | ✓ |  |
 `x86_64-uwp-windows-msvc` | ✓ |  |
 `x86_64-wrs-vxworks` | ? |  |
-`x86_64h-apple-darwin` | ✓ | ✓ | macOS with late-gen Intel (at least Haswell)
+[`x86_64h-apple-darwin`](platform-support/x86_64h-apple-darwin.md) | ✓ | ✓ | macOS with late-gen Intel (at least Haswell)
 
 [runs on NVIDIA GPUs]: https://github.com/japaric-archived/nvptx#targets