Add #includes so that ROCm.h is compilable stand-alone.

[saugustine]

Summary

ROCm.h had been getting the declarations for various data structures
by being #included next to them, rather than #includeing them itself.

This change fixes that by explicitly including the appropriate headers.

[saugustine]

For post-commit review.

[jyknight]

LGTM.

clang/lib/Driver/ToolChains/ROCm.h

 //===--- ROCm.h - ROCm installation detector --------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_ROCM_H
 #define LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_ROCM_H
 
 #include "clang/Basic/Cuda.h"
+#include "clang/Basic/LLVM.h"
+#include "clang/Driver/Driver.h"
 #include "clang/Driver/Options.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Option/ArgList.h"
 
 namespace clang {
 namespace driver {
 
 /// A class to find a viable ROCM installation
 /// TODO: Generalize to handle libclc.
 class RocmInstallationDetector {
 private: