[libclang] Make the test portable.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145377 91177308-0d34-0410-b5e6-96231b3b80d8

test/Index/file-macro-refs.c

@@ -4,7 +4,7 @@ FOO
 FOO
 
 // RUN: c-index-test -file-refs-at=%s:3:2 %s | FileCheck %s
-// RUN: CINDEXTEST_EDITING=1 c-index-test -file-refs-at=%s:3:2 %s | FileCheck %s
+// RUN: env CINDEXTEST_EDITING=1 c-index-test -file-refs-at=%s:3:2 %s | FileCheck %s
 
 // CHECK:      macro expansion=FOO:1:9
 // CHECK-NEXT: macro definition=FOO =[1:9 - 1:12]