[Clang][AMDGPU] Search both amdgcn and amdgpu libraries (#209770)

Summary:
Temporary workaround as we transition triples from amdgcn to amdgpu.

Author: jhuber6

clang/lib/Driver/ToolChain.cpp

@@ -1122,6 +1122,14 @@ ToolChain::getTargetSubDirPath(StringRef BaseDir) const {
   if (auto Path = getPathForTriple(T))
     return *Path;
 
+  // Handle the legacy AMDGPU triple case as well.
+  if (T.getArchName() == "amdgcn") {
+    llvm::Triple Canon(T);
+    Canon.setArchName("amdgpu");
+    if (auto Path = getPathForTriple(Canon))
+      return *Path;
+  }
+
   if (T.isOSAIX()) {
     llvm::Triple AIXTriple;
     if (T.getEnvironment() == Triple::UnknownEnvironment) {

clang/test/Driver/Inputs/resource_dir_with_amdgpu_per_target_subdir/lib/amdgpu-amd-amdhsa/libclang_rt.profile.a

@@ -71,3 +71,9 @@
 // RUN:   | FileCheck -check-prefixes=UBSAN %s
 //      UBSAN: ld.lld
 // UBSAN-SAME: "[[RESOURCE_DIR:.+]]{{/|\\\\}}lib{{/|\\\\}}amdgcn-amd-amdhsa{{/|\\\\}}libclang_rt.ubsan_minimal.a"
+
+// RUN: %clang -### --target=amdgcn-amd-amdhsa -mcpu=gfx906 -nogpulib \
+// RUN:   -resource-dir=%S/Inputs/resource_dir_with_amdgpu_per_target_subdir \
+// RUN:   -fprofile-generate %s 2>&1 | FileCheck -check-prefixes=PROFILE-AMDGPU %s
+//      PROFILE-AMDGPU: ld.lld
+// PROFILE-AMDGPU-SAME: "[[RESOURCE_DIR:.+]]{{/|\\\\}}lib{{/|\\\\}}amdgpu-amd-amdhsa{{/|\\\\}}libclang_rt.profile.a"