Add back the removed pair of "#ifndef VA_START" and "#endif" in recent check-in to avoid macro redefinition.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@10595 6f19259b-4bc3-4df7-8a09-765794883524

EdkCompatibilityPkg/Foundation/Include/EfiStdArg.h

@@ -108,6 +108,9 @@ typedef __builtin_va_list VA_LIST;
 #define VA_END(Marker)               __builtin_va_end (Marker)
 
 #else
+
+#ifndef VA_START
+
 ///
 /// Variable used to traverse the list of arguments. This type can vary by 
 /// implementation and could be an array or structure. 
@@ -165,3 +168,5 @@ typedef CHAR8 *VA_LIST;
 #endif
 
 #endif
+
+#endif