tests: Add loongarch64-unknown-linux-musl target

Author: heiher

tests/assembly/targets/targets-elf.rs

@@ -234,6 +234,9 @@
 //@ revisions: loongarch64_unknown_linux_gnu
 //@ [loongarch64_unknown_linux_gnu] compile-flags: --target loongarch64-unknown-linux-gnu
 //@ [loongarch64_unknown_linux_gnu] needs-llvm-components: loongarch
+//@ revisions: loongarch64_unknown_linux_musl
+//@ [loongarch64_unknown_linux_musl] compile-flags: --target loongarch64-unknown-linux-musl
+//@ [loongarch64_unknown_linux_musl] needs-llvm-components: loongarch
 //@ revisions: loongarch64_unknown_none
 //@ [loongarch64_unknown_none] compile-flags: --target loongarch64-unknown-none
 //@ [loongarch64_unknown_none] needs-llvm-components: loongarch