Specify clang exe path in Driver Creation

By doing so, TheDriver can get the correct resource dir.

Closes: ROCm#48
Reference: ROCm#49

lib/comgr/src/comgr-compiler.cpp

@@ -660,7 +660,7 @@ AMDGPUCompiler::executeInProcessDriver(ArrayRef<const char *> Args) {
   IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs);
   DiagnosticsEngine Diags(DiagID, &*DiagOpts, DiagClient);
   ProcessWarningOptions(Diags, *DiagOpts, /*ReportDiags=*/false);
-  Driver TheDriver("", "", Diags);
+  Driver TheDriver((Twine(env::getLLVMPath()) + "/bin/clang").str(), "", Diags);
   TheDriver.setTitle("AMDGPU Code Object Manager");
   TheDriver.setCheckInputsExist(false);
 
@@ -998,11 +998,6 @@ amd_comgr_status_t AMDGPUCompiler::addCompilationFlags() {
   HIPIncludePath = (Twine(env::getHIPPath()) + "/include").str();
   // HIP headers depend on hsa.h which is in ROCM_DIR/include.
   ROCMIncludePath = (Twine(env::getROCMPath()) + "/include").str();
-  ClangIncludePath =
-      (Twine(env::getLLVMPath()) + "/lib/clang/" + CLANG_VERSION_STRING).str();
-  ClangIncludePath2 = (Twine(env::getLLVMPath()) + "/lib/clang/" +
-                       CLANG_VERSION_STRING + "/include")
-                          .str();
 
   Args.push_back("-x");
 
@@ -1028,10 +1023,6 @@ amd_comgr_status_t AMDGPUCompiler::addCompilationFlags() {
     Args.push_back(ROCMIncludePath.c_str());
     Args.push_back("-isystem");
     Args.push_back(HIPIncludePath.c_str());
-    Args.push_back("-isystem");
-    Args.push_back(ClangIncludePath.c_str());
-    Args.push_back("-isystem");
-    Args.push_back(ClangIncludePath2.c_str());
     break;
   default:
     return AMD_COMGR_STATUS_ERROR_INVALID_ARGUMENT;