[builtins] Use libtool for builtins when building for Apple platform

[phosek]

Summary

compiler-rt already uses libtool instead of ar when building for
Apple platform, but that's not being used when builtins are being
built separately e.g. as part of the runtimes build. This change
extracts the logic setting up libtool into a separate file and uses
it from both the compiler-rt and standalone builtins build.

[beanz]

LGTM

compiler-rt/CMakeLists.txt

if (COMPILER_RT_STANDALONE_BUILD)
   include(FindPythonInterp)
   if(NOT PYTHONINTERP_FOUND)
     message(FATAL_ERROR "
       Unable to find Python interpreter required testing. Please install Python
       or specify the PYTHON_EXECUTABLE CMake variable.")
   endif()
 
   # Ensure that fat libraries are built correctly on Darwin
-  if(CMAKE_SYSTEM_NAME STREQUAL Darwin)
-    if(NOT CMAKE_LIBTOOL)
-      find_program(CMAKE_XCRUN
-                   NAMES
-                     xcrun)
-      if(CMAKE_XCRUN)
-        execute_process(COMMAND
-                          ${CMAKE_XCRUN} -find libtool
-                        OUTPUT_VARIABLE
-                          CMAKE_LIBTOOL
-                        OUTPUT_STRIP_TRAILING_WHITESPACE)
-      endif()
-
-      if(NOT CMAKE_LIBTOOL OR NOT EXISTS CMAKE_LIBTOOL)
-        find_program(CMAKE_LIBTOOL
-                     NAMES
-                       libtool)
-      endif()
-    endif()
-
-    get_property(languages GLOBAL PROPERTY ENABLED_LANGUAGES)
-
-    if(CMAKE_LIBTOOL)
-      set(CMAKE_LIBTOOL ${CMAKE_LIBTOOL} CACHE PATH "libtool executable")
-      message(STATUS "Found libtool - ${CMAKE_LIBTOOL}")
-
-      execute_process(COMMAND
-                        ${CMAKE_LIBTOOL} -V
-                      OUTPUT_VARIABLE
-                        LIBTOOL_V_OUTPUT
-                      OUTPUT_STRIP_TRAILING_WHITESPACE)
-      if("${LIBTOOL_V_OUTPUT}" MATCHES ".*cctools-([0-9]+).*")
-        string(REGEX REPLACE ".*cctools-([0-9]+).*" "\\1" LIBTOOL_VERSION ${LIBTOOL_V_OUTPUT})
-        if(NOT LIBTOOL_VERSION VERSION_LESS "862")
-          set(LIBTOOL_NO_WARNING_FLAG "-no_warning_for_no_symbols")
-        endif()
-      endif()
-
-      foreach(lang ${languages})
-        set(CMAKE_${lang}_CREATE_STATIC_LIBRARY "\"${CMAKE_LIBTOOL}\" -static ${LIBTOOL_NO_WARNING_FLAG} -o <TARGET> <LINK_FLAGS> <OBJECTS>")
-      endforeach()
-    endif()
-
-    # Workaround SIP :-(
-    if(DYLD_LIBRARY_PATH)
-      set(dyld_envar "DYLD_LIBRARY_PATH=${DYLD_LIBRARY_PATH}")
-      foreach(lang ${languages})
-        foreach(cmd ${CMAKE_${lang}_CREATE_STATIC_LIBRARY})
-          list(APPEND CMAKE_${lang}_CREATE_STATIC_LIBRARY_NEW "${dyld_envar} ${cmd}")
-        endforeach()
-      endforeach()
-    endif()
+  if(CMAKE_HOST_APPLE AND APPLE)
+    include(UseLibtool)
   endif()
 
   # Define default arguments to lit.
   set(LIT_ARGS_DEFAULT "-sv")
   if (MSVC OR XCODE)
     set(LIT_ARGS_DEFAULT "${LIT_ARGS_DEFAULT} --no-progress-bar")
   endif()
   set(LLVM_LIT_ARGS "${LIT_ARGS_DEFAULT}" CACHE STRING "Default options for lit")

compiler-rt/cmake/Modules/UseLibtool.cmake

+# if CMAKE_LIBTOOL is not set, try and find it with xcrun or find_program
+if(NOT CMAKE_LIBTOOL)
+  if(NOT CMAKE_XCRUN)
+    find_program(CMAKE_XCRUN NAMES xcrun)
+  endif()
+  if(CMAKE_XCRUN)
+    execute_process(COMMAND ${CMAKE_XCRUN} -find libtool
+      OUTPUT_VARIABLE CMAKE_LIBTOOL
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+  endif()
+
+  if(NOT CMAKE_LIBTOOL OR NOT EXISTS CMAKE_LIBTOOL)
+    find_program(CMAKE_LIBTOOL NAMES libtool)
+  endif()
+endif()
+
+get_property(languages GLOBAL PROPERTY ENABLED_LANGUAGES)
+if(CMAKE_LIBTOOL)
+  set(CMAKE_LIBTOOL ${CMAKE_LIBTOOL} CACHE PATH "libtool executable")
+  message(STATUS "Found libtool - ${CMAKE_LIBTOOL}")
+
+  execute_process(COMMAND ${CMAKE_LIBTOOL} -V
+    OUTPUT_VARIABLE LIBTOOL_V_OUTPUT
+    OUTPUT_STRIP_TRAILING_WHITESPACE)
+  if("${LIBTOOL_V_OUTPUT}" MATCHES ".*cctools-([0-9.]+).*")
+    string(REGEX REPLACE ".*cctools-([0-9.]+).*" "\\1" LIBTOOL_VERSION
+      ${LIBTOOL_V_OUTPUT})
+    if(NOT LIBTOOL_VERSION VERSION_LESS "862")
+      set(LIBTOOL_NO_WARNING_FLAG "-no_warning_for_no_symbols")
+    endif()
+  endif()
+
+  foreach(lang ${languages})
+    set(CMAKE_${lang}_CREATE_STATIC_LIBRARY
+      "\"${CMAKE_LIBTOOL}\" -static ${LIBTOOL_NO_WARNING_FLAG} -o <TARGET> <LINK_FLAGS> <OBJECTS>")
+  endforeach()
+endif()
+
+# If DYLD_LIBRARY_PATH is set we need to set it on archiver commands
+if(DYLD_LIBRARY_PATH)
+  set(dyld_envar "DYLD_LIBRARY_PATH=${DYLD_LIBRARY_PATH}")
+  foreach(lang ${languages})
+    foreach(cmd ${CMAKE_${lang}_CREATE_STATIC_LIBRARY})
+      list(APPEND CMAKE_${lang}_CREATE_STATIC_LIBRARY_NEW
+           "${dyld_envar} ${cmd}")
+    endforeach()
+    set(CMAKE_${lang}_CREATE_STATIC_LIBRARY
+      ${CMAKE_${lang}_CREATE_STATIC_LIBRARY_NEW})
+  endforeach()
+endif()

compiler-rt/lib/builtins/CMakeLists.txt

if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   include(CompilerRTUtils)
 
   load_llvm_config()
   construct_compiler_rt_default_triple()
 
   if(APPLE)
     include(CompilerRTDarwinUtils)
   endif()
+  if(CMAKE_HOST_APPLE AND APPLE)
+    include(UseLibtool)
+  endif()
   include(AddCompilerRT)
 endif()
 
 include(builtin-config-ix)
 
 # TODO: Need to add a mechanism for logging errors when builtin source files are
 # added to a sub-directory and not this CMakeLists file.
 set(GENERIC_SOURCES