libprofile/CommonProfiling.c: Fix according to C89.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167272 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/runtime/libprofile/CommonProfiling.c b/runtime/libprofile/CommonProfiling.c
index 058270b..8f4119c 100644
--- a/runtime/libprofile/CommonProfiling.c
+++ b/runtime/libprofile/CommonProfiling.c
@@ -36,10 +36,10 @@
  * variable is set.  If it is then save it and set OutputFilename.
  */
 static void check_environment_variable(void) {
+  const char *EnvVar;
   if (SavedEnvVar) return; /* Guarantee that we can't leak memory. */
 
-  const char *EnvVar = getenv("LLVMPROF_OUTPUT");
-  if (EnvVar) {
+  if ((EnvVar = getenv("LLVMPROF_OUTPUT")) != NULL) {
     /* The string that getenv returns is allowed to be statically allocated,
      * which means it may be changed by future calls to getenv, so copy it.
      */