Merge pull request swiftlang#28769 from apple/shahmishal/env-c-launcher

[Build System] Add support to set C and CXX launcher with env …

Author: shahmishal

utils/build_swift/driver_arguments.py

@@ -8,6 +8,7 @@
 
 
 import multiprocessing
+import os
 
 import android.adb.commands
 
@@ -380,8 +381,10 @@ def create_argument_parser():
            help='the absolute path to CXX, the "clang++" compiler for the '
                 'host platform. Default is auto detected.')
     option('--cmake-c-launcher', store_path(executable=True),
+           default=os.environ.get('C_COMPILER_LAUNCHER', None),
            help='the absolute path to set CMAKE_C_COMPILER_LAUNCHER')
     option('--cmake-cxx-launcher', store_path(executable=True),
+           default=os.environ.get('CXX_COMPILER_LAUNCHER', None),
            help='the absolute path to set CMAKE_CXX_COMPILER_LAUNCHER')
     option('--host-lipo', store_path(executable=True),
            help='the absolute path to lipo. Default is auto detected.')