common: Silence -Wunused-function clang warnings. (#3127)

v2: Use pragma instead of [[maybe_unused]].
v3: Silence warnings with older clang versions too.

common/include/Utilities/gtkGuiTools.h

@@ -34,6 +34,11 @@
 // on what it's built for.
 //
 
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-function"
+#endif
+
 static GtkWidget *ps_gtk_hbox_new(int padding = 5)
 {
 #if GTK_MAJOR_VERSION < 3
@@ -131,3 +136,7 @@ static void pcsx2_message(const wchar_t *fmt, ...)
     gtk_dialog_run(GTK_DIALOG(dialog));
     gtk_widget_destroy(dialog);
 }
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif

common/include/x86emitter/x86_intrin.h

@@ -69,16 +69,21 @@ static __inline__ __attribute__((always_inline)) unsigned long long xgetbv(unsig
 
 // Rotate instruction
 #if defined(__clang__) && __clang_major__ < 9
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-function"
+
 // Seriously what is so complicated to provided this bunch of intrinsics in clangs.
-[[maybe_unused]] static unsigned int _rotr(unsigned int x, int s)
+static unsigned int _rotr(unsigned int x, int s)
 {
     return (x >> s) | (x << (32 - s));
 }
 
-[[maybe_unused]] static unsigned int _rotl(unsigned int x, int s)
+static unsigned int _rotl(unsigned int x, int s)
 {
     return (x << s) | (x >> (32 - s));
 }
+
+#pragma clang diagnostic pop
 #endif
 
 // Not correctly defined in GCC4.8 and below ! (dunno for VS)