Workaround for libc++ include path for HIP-Clang (#1917)

HIP-Clang cuda_wrapper headers require clang include path before standard C++ include path.
However libc++ include path requires to be before clang include path.
To workaround this, we pass -isystem with the parent directory of clang include
path instead of the clang include path itself.

bin/hipcc

@@ -207,7 +207,7 @@ if ($HIP_PLATFORM eq "clang") {
     } else {
       $HIPCXXFLAGS .= " -std=c++11";
     }
-    $HIPCXXFLAGS .= " -isystem $HIP_CLANG_INCLUDE_PATH";
+    $HIPCXXFLAGS .= " -isystem $HIP_CLANG_INCLUDE_PATH/..";
     $HIPLDFLAGS .= " -L$HIP_LIB_PATH";
     if (not $isWindows) {
       $HIPLDFLAGS .= " -Wl,--rpath-link=$HIP_LIB_PATH";