Rollup merge of #77950 - arlosi:sha256, r=eddyb

Add support for SHA256 source file hashing

Adds support for `-Z src-hash-algorithm sha256`, which became available in LLVM 11.

Using an older version of LLVM will cause an error `invalid checksum kind` if the hash algorithm is set to sha256.

r? `@eddyb`
cc #70401 `@est31`

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -648,6 +648,7 @@ enum class LLVMRustChecksumKind {
   None,
   MD5,
   SHA1,
+  SHA256,
 };
 
 static Optional<DIFile::ChecksumKind> fromRust(LLVMRustChecksumKind Kind) {
@@ -658,6 +659,10 @@ static Optional<DIFile::ChecksumKind> fromRust(LLVMRustChecksumKind Kind) {
     return DIFile::ChecksumKind::CSK_MD5;
   case LLVMRustChecksumKind::SHA1:
     return DIFile::ChecksumKind::CSK_SHA1;
+#if (LLVM_VERSION_MAJOR >= 11)
+  case LLVMRustChecksumKind::SHA256:
+    return DIFile::ChecksumKind::CSK_SHA256;
+#endif
   default:
     report_fatal_error("bad ChecksumKind.");
   }