DebugLib: Simplify DEBUG macro used when MDEPKG_NDEBUG is defined

The variant used when MDEPKG_NDEBUG is defined will be optimised
away in RELEASE builds, but by referencing the argument list, avoids
unused variable errors from valid debug code, for example when STATIC
variables are used only in DEBUG statements.

MdePkg/Include/Library/DebugLib.h

@@ -433,18 +433,13 @@ UnitTestDebugAssert (
         _DEBUG (Expression);       \
       }                            \
     } while (FALSE)
-#elif defined (__GNUC__) || defined (__clang__)
-#define DEBUG(Expression)                                \
-    do {                                                   \
-      _Pragma("GCC diagnostic push")                       \
-      _Pragma("GCC diagnostic ignored \"-Wunused-value\"") \
-      if ((FALSE)) {                                       \
-        (VOID) Expression;                                 \
-      }                                                    \
-      _Pragma("GCC diagnostic pop")                        \
-    } while (FALSE)
 #else
-#define DEBUG(Expression)
+#define DEBUG(Expression)        \
+    do {                           \
+      if (FALSE) {                 \
+        _DEBUG (Expression);       \
+      }                            \
+    } while (FALSE)
 #endif
 
 /**