Rollup merge of #149312 - mati865:push-uxlynzmxzswo, r=wesleywiser

Mark riscv64gc-unknown-linux-musl as tier 2 target

According to cdb4236e65/src/doc/rustc/src/platform-support/riscv64gc-unknown-linux-musl.md (L3) it's tier 2 target.

In case you are wondering how I noticed it:
Dockerfiles at Wild linker repo started to fail building recently due to missing `riscv64gc-unknown-linux-musl` std. I had hoped the problem would go away by itself, but it did not (it never does...).
https://github.com/rust-lang/rust/pull/148983 happened recently, so I checked https://rust-lang.github.io/rustup-components-history/riscv64gc-unknown-linux-musl.html and yeah, the date matches.
Given this condition: cdb4236e65/src/tools/build-manifest/build.rs (L35) I'm certain PR will fix the problem.

compiler/rustc_target/src/spec/targets/riscv64gc_unknown_linux_musl.rs

@@ -7,7 +7,7 @@ pub(crate) fn target() -> Target {
         llvm_target: "riscv64-unknown-linux-musl".into(),
         metadata: TargetMetadata {
             description: Some("RISC-V Linux (kernel 4.20, musl 1.2.5)".into()),
-            tier: Some(3),
+            tier: Some(2),
             host_tools: Some(false),
             std: Some(true),
         },