[lit] Pass more environment variables through to child processes.

This arose when I was trying to have a substitution which invoked a
python script P, and that python script tried to invoke clang-cl (or
even cl). Since we invoke P with a custom environment, it doesn't
inherit the environment of the parent, and then when we go to invoke
clang-cl, it's unable to find the MSVC installation directory. There
were many more I could have passed through which are set by vcvarsall,
but I tried to keep it simple and only pass through the important ones.

Differential Revision: https://reviews.llvm.org/D54963

llvm-svn: 347691

llvm/utils/lit/lit/TestingConfig.py

@@ -26,7 +26,16 @@ class TestingConfig:
                      'LSAN_OPTIONS', 'ADB', 'ANDROID_SERIAL',
                      'SANITIZER_IGNORE_CVE_2016_2143', 'TMPDIR', 'TMP', 'TEMP',
                      'TEMPDIR', 'AVRLIT_BOARD', 'AVRLIT_PORT',
-                     'FILECHECK_DUMP_INPUT_ON_FAILURE', 'FILECHECK_OPTS']
+                     'FILECHECK_DUMP_INPUT_ON_FAILURE', 'FILECHECK_OPTS',
+                     'VCINSTALLDIR', 'VCToolsinstallDir', 'VSINSTALLDIR',
+                     'WindowsSdkDir', 'WindowsSDKLibVersion']
+
+        if sys.platform == 'win32':
+            pass_vars.append('INCLUDE')
+            pass_vars.append('LIB')
+            pass_vars.append('PATHEXT')
+            environment['PYTHONBUFFERED'] = '1'
+
         for var in pass_vars:
             val = os.environ.get(var, '')
             # Check for empty string as some variables such as LD_PRELOAD cannot be empty
@@ -34,15 +43,6 @@ class TestingConfig:
             if val:
                 environment[var] = val
 
-        if sys.platform == 'win32':
-            environment.update({
-                    'INCLUDE' : os.environ.get('INCLUDE',''),
-                    'PATHEXT' : os.environ.get('PATHEXT',''),
-                    'PYTHONUNBUFFERED' : '1',
-                    'TEMP' : os.environ.get('TEMP',''),
-                    'TMP' : os.environ.get('TMP',''),
-                    })
-
         # Set the default available features based on the LitConfig.
         available_features = []
         if litConfig.useValgrind: