[CMake] Build runtimes for Fuchsia targets

[phosek]

Summary

This relies on the multi-target runtimes build support.

[beanz]

This all looks great. I'm really excited to have such a complete toolchain build example in-tree. Thank you!

cmake/caches/Fuchsia-stage2.cmake

 # This file sets up a CMakeCache for the second stage of a Fuchsia toolchain
 # build.
 
 set(LLVM_TARGETS_TO_BUILD X86;ARM;AArch64 CACHE STRING "")
 
 set(PACKAGE_VENDOR Fuchsia CACHE STRING "")
 
 set(LLVM_INCLUDE_EXAMPLES OFF CACHE BOOL "")
 set(LLVM_INCLUDE_DOCS OFF CACHE BOOL "")
-set(LLVM_TOOL_CLANG_TOOLS_EXTRA_BUILD OFF CACHE BOOL "")
 set(LLVM_ENABLE_ZLIB ON CACHE BOOL "")
 set(LLVM_ENABLE_BACKTRACES OFF CACHE BOOL "")
 set(LLVM_EXTERNALIZE_DEBUGINFO ON CACHE BOOL "")
 set(CLANG_PLUGIN_SUPPORT OFF CACHE BOOL "")
 
 set(LLVM_ENABLE_LTO ON CACHE BOOL "")
 if(NOT APPLE)
   set(LLVM_ENABLE_LLD ON CACHE BOOL "")
   set(CLANG_DEFAULT_LINKER lld CACHE STRING "")
 endif()
 
 if(APPLE)
   set(LLDB_CODESIGN_IDENTITY "" CACHE STRING "")
 endif()
 
 set(CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
 set(CMAKE_C_FLAGS_RELWITHDEBINFO "-O2 -gline-tables-only -DNDEBUG" CACHE STRING "")
 set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2 -gline-tables-only -DNDEBUG" CACHE STRING "")
 
-set(LLVM_BUILTIN_TARGETS "x86_64-fuchsia-none;aarch64-fuchsia-none" CACHE STRING "")
-set(BUILTINS_x86_64-fuchsia-none_CMAKE_SYSROOT ${FUCHSIA_SYSROOT} CACHE STRING "")
-set(BUILTINS_x86_64-fuchsia-none_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
-set(BUILTINS_aarch64-fuchsia-none_CMAKE_SYSROOT ${FUCHSIA_SYSROOT} CACHE STRING "")
-set(BUILTINS_aarch64-fuchsia-none_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
+set(LLVM_BUILTIN_TARGETS "x86_64-fuchsia;aarch64-fuchsia" CACHE STRING "")
+foreach(target x86_64;aarch64)
+  set(BUILTINS_${target}-fuchsia_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
+  set(BUILTINS_${target}-fuchsia_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
+endforeach()
+if(NOT APPLE)
+  list(APPEND LLVM_BUILTIN_TARGETS "default")
+endif()
+
+set(LLVM_RUNTIME_TARGETS "default;x86_64-fuchsia;aarch64-fuchsia" CACHE STRING "")
+foreach(target x86_64;aarch64)
+  set(RUNTIMES_${target}-fuchsia_CMAKE_BUILD_WITH_INSTALL_RPATH ON CACHE BOOL "")
+  set(RUNTIMES_${target}-fuchsia_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
+  set(RUNTIMES_${target}-fuchsia_CMAKE_SYSTEM_NAME Fuchsia CACHE STRING "")
+  set(RUNTIMES_${target}-fuchsia_UNIX 1 CACHE BOOL "")
+  set(RUNTIMES_${target}-fuchsia_LLVM_ENABLE_LIBCXX ON CACHE BOOL "")
+  set(RUNTIMES_${target}-fuchsia_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
+  set(RUNTIMES_${target}-fuchsia_LIBCXXABI_USE_COMPILER_RT ON CACHE BOOL "")
+  set(RUNTIMES_${target}-fuchsia_LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
+  set(RUNTIMES_${target}-fuchsia_LIBCXX_USE_COMPILER_RT ON CACHE BOOL "")
+endforeach()
 
 # Setup toolchain.
 set(LLVM_INSTALL_TOOLCHAIN_ONLY ON CACHE BOOL "")
 set(LLVM_TOOLCHAIN_TOOLS
   llc
   llvm-ar
   llvm-cov
   llvm-cxxfilt
   llvm-dwarfdump
   llvm-dsymutil
   llvm-lib
   llvm-nm
   llvm-objdump
   llvm-profdata
   llvm-ranlib
+  llvm-readelf
   llvm-readobj
   llvm-size
   llvm-symbolizer
   opt
   CACHE STRING "")
 
 set(LLVM_DISTRIBUTION_COMPONENTS
   clang
   lld
   lldb
   liblldb
   LTO
   clang-format
   clang-headers
-  builtins-x86_64-fuchsia-none
-  builtins-aarch64-fuchsia-none
+  clang-tidy
+  clangd
+  builtins
   runtimes
   ${LLVM_TOOLCHAIN_TOOLS}
   CACHE STRING "")

cmake/caches/Fuchsia.cmake

set(CLANG_BOOTSTRAP_TARGETS
   test-suite
   test-depends
   llvm-test-depends
   clang-test-depends
   distribution
   install-distribution
   clang CACHE STRING "")
 
-if(FUCHSIA_SYSROOT)
-  set(EXTRA_ARGS -DFUCHSIA_SYSROOT=${FUCHSIA_SYSROOT})
+foreach(target x86_64;aarch64)
+  if(FUCHSIA_${target}_SYSROOT)
+    list(APPEND EXTRA_ARGS -DFUCHSIA_${target}_SYSROOT=${FUCHSIA_${target}_SYSROOT})
   endif()
+endforeach()
 
 # Setup the bootstrap build.
 set(CLANG_ENABLE_BOOTSTRAP ON CACHE BOOL "")
 set(CLANG_BOOTSTRAP_CMAKE_ARGS
   ${EXTRA_ARGS}
   -C ${CMAKE_CURRENT_LIST_DIR}/Fuchsia-stage2.cmake
   CACHE STRING "")