CmpDriver: Allow over-ride of drivers to compare through env variables
(DRIVER_[AB]).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@62242 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/CmpDriver b/utils/CmpDriver
index 137f60b..9301ed7 100755
--- a/utils/CmpDriver
+++ b/utils/CmpDriver
@@ -126,11 +126,11 @@
     return CompileInfo(out,err,res)
 
 def main():
-    import sys
+    import os, sys
 
     args = sys.argv[1:]
-    driverA = 'gcc'
-    driverB = 'xcc'
+    driverA = os.getenv('DRIVER_A') or 'gcc'
+    driverB = os.getenv('DRIVER_B') or 'xcc'
 
     infoA = captureDriverInfo(driverA, args)
     infoB = captureDriverInfo(driverB, args)