LLVM_LTO support for make / ninja

pylib/gyp/xcode_emulation.py

 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 This module contains classes that help to emulate xcodebuild behavior on top of
 other build systems, such as make and ninja.
 """
 
 import gyp.common
@@ skipping 281 matching lines @@
 
     if self._Test('GCC_SYMBOLS_PRIVATE_EXTERN', 'YES', default='NO'):
       cflags.append('-fvisibility=hidden')
 
     if self._Test('GCC_TREAT_WARNINGS_AS_ERRORS', 'YES', default='NO'):
       cflags.append('-Werror')
 
     if self._Test('GCC_WARN_ABOUT_MISSING_NEWLINE', 'YES', default='NO'):
       cflags.append('-Wnewline-eof')
 
+    # In Xcode, this is only activated when GCC_COMPILER_VERSION is clang or
+    # llvm-gcc. It also requires a fairly recent libtool, and
+    # if the system clang isn't used, DYLD_LIBRARY_PATH needs to contain the
+    # path to the libLTO.dylib that matches the used clang.
+    if self._Test('LLVM_LTO', 'YES', default='NO'):
+      cflags.append('-flto')
+
     self._Appendf(cflags, 'MACOSX_DEPLOYMENT_TARGET', '-mmacosx-version-min=%s')
 
     # TODO:
     if self._Test('COPY_PHASE_STRIP', 'YES', default='NO'):
       self._WarnUnimplemented('COPY_PHASE_STRIP')
     self._WarnUnimplemented('GCC_DEBUGGING_SYMBOLS')
     self._WarnUnimplemented('GCC_ENABLE_OBJC_EXCEPTIONS')
     self._WarnUnimplemented('GCC_ENABLE_OBJC_GC')
 
     # TODO: This is exported correctly, but assigning to it is not supported.
@@ skipping 676 matching lines @@
     # absolutified. Else, it's in the PATH (e.g. install_name_tool, ln).
     if os.path.sep in shell_list[0]:
       shell_list[0] = gyp_path_to_build_path(shell_list[0])
 
       # "script.sh" -> "./script.sh"
       if not os.path.sep in shell_list[0]:
         shell_list[0] = os.path.join('.', shell_list[0])
     postbuilds.append(gyp.common.EncodePOSIXShellList(shell_list))
 
   return postbuilds