[Clang][CMake] Set up distribution target for Clang-BOLT

Provide a way to install usable BOLT-optimized Clang
(clang + resource headers) using
`ninja clang-bolt install-distribution` with BOLT.cmake cache file
or `ninja stage2-clang-bolt stage2-install-distribution`
with BOLT-PGO.cmake cache file.

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D140565

Author: aaupov

clang/cmake/caches/BOLT-PGO.cmake

@@ -2,10 +2,16 @@ set(LLVM_ENABLE_PROJECTS "bolt;clang;lld" CACHE STRING "")
 
 set(CLANG_BOOTSTRAP_TARGETS
   stage2-clang-bolt
+  stage2-distribution
+  stage2-install-distribution
   CACHE STRING "")
 set(BOOTSTRAP_CLANG_BOOTSTRAP_TARGETS
   clang-bolt
+  distribution
+  install-distribution
   CACHE STRING "")
 
-set(PGO_BUILD_CONFIGURATION ${CMAKE_CURRENT_LIST_DIR}/BOLT.cmake CACHE STRING "")
+set(PGO_BUILD_CONFIGURATION
+  ${CMAKE_CURRENT_LIST_DIR}/BOLT.cmake
+  CACHE STRING "")
 include(${CMAKE_CURRENT_LIST_DIR}/PGO.cmake)

clang/cmake/caches/BOLT.cmake

@@ -8,6 +8,13 @@ set(CLANG_BOLT_INSTRUMENT_EXTRA_CMAKE_FLAGS "" CACHE STRING "")
 set(LLVM_ENABLE_PROJECTS "bolt;clang" CACHE STRING "")
 set(LLVM_TARGETS_TO_BUILD Native CACHE STRING "")
 
+# setup toolchain
+set(LLVM_INSTALL_TOOLCHAIN_ONLY ON CACHE BOOL "")
+set(LLVM_DISTRIBUTION_COMPONENTS
+  clang
+  clang-resource-headers
+  CACHE STRING "")
+
 # Disable function splitting enabled by default in GCC8+
 if("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fno-reorder-blocks-and-partition")