rustc_target: Mark UEFI targets as is_like_windows/is_like_msvc

Document what `is_like_windows` and `is_like_msvc` mean in more detail.

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -925,9 +925,7 @@ unsafe fn embed_bitcode(
         || cgcx.opts.target_triple.triple().starts_with("asmjs")
     {
         // nothing to do here
-    } else if cgcx.opts.target_triple.triple().contains("windows")
-        || cgcx.opts.target_triple.triple().contains("uefi")
-    {
+    } else if cgcx.is_pe_coff {
         let asm = "
             .section .llvmbc,\"n\"
             .section .llvmcmd,\"n\"