Expose ROCm path option in top CMake

This allows the compiler to compile against a custom ROCm location,
not just /opt/rocm.
This options is use during compilation of the ROCm ukernels.

CMakeLists.txt

@@ -364,6 +364,10 @@ cmake_dependent_option(IREE_TARGET_BACKEND_VULKAN_SPIRV "Enables the 'vulkan-spi
 # Default target backends that are not yet fully supported but are being brought up.
 cmake_dependent_option(IREE_TARGET_BACKEND_ROCM "Enables the 'rocm' compiler target backend" ${IREE_TARGET_BACKEND_DEFAULTS} ${IREE_BUILD_COMPILER} OFF)
 
+set(CMAKE_CXX_FLAGS_FASTBUILD "-gmlt" CACHE STRING "Flags used by the C++ compiler during fast builds." FORCE)
+set(IREE_ROCM_PATH_DEFAULT "/opt/rocm")
+set(IREE_ROCM_PATH "${IREE_ROCM_PATH_DEFAULT}" CACHE STRING "Path to ROCm installation.")
+
 # Supported default target backends that are only available on certain
 # platforms.
 set(IREE_TARGET_BACKEND_CUDA_DEFAULT ${IREE_TARGET_BACKEND_DEFAULTS})

compiler/plugins/target/ROCM/builtins/ukernel/CMakeLists.txt

@@ -10,9 +10,6 @@ endif()
 # Check if HIP is installed on system.
 # HIP is required to compile ukernels.
 # TODO: We can do better than this and ensure that headers are always available.
-if (NOT IREE_ROCM_PATH)
-  set(IREE_ROCM_PATH "/opt/rocm")
-endif()
 set (IREE_ROCM_VERSION "${IREE_ROCM_PATH}/.info/version")
 if (NOT EXISTS ${IREE_ROCM_VERSION})
   message(STATUS
@@ -57,6 +54,7 @@ function(iree_rocm_bitcode_library)
     # Suppress warnings about missing path to rocm lib,
     # and benign warning about ROCM version.
     "-nogpulib"
+    "--rocm-path=${IREE_ROCM_PATH}"
     "-D_ALLOW_COMPILER_AND_STL_VERSION_MISMATCH"
     # Avoid error caused by clang bundling.
     "--offload-device-only"