Bug 336183 [arm build] undefined reference _PrepareAndDispatch in xpcom_core

This is a GCC3.4 fix over a previous GCC fix it obsoletes the poorlly designed
patch which was written for bug 307418

moa=timeless

xpcom/reflect/xptcall/src/md/unix/xptcstubs_arm.cpp

@@ -44,9 +44,21 @@
 #error "This code is for Linux ARM only. Please check if it works for you, too.\nDepends strongly on gcc behaviour."
 #endif
 
+#if (__GNUC__ > 3) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))
+/* This tells gcc3.4+ not to optimize away symbols.
+ * @see http://gcc.gnu.org/gcc-3.4/changes.html
+ */
+#define DONT_DROP_OR_WARN __attribute__(used)
+#else
+/* This tells older gccs not to warn about unused vairables.
+ * @see http://docs.freebsd.org/info/gcc/gcc.info.Variable_Attributes.html
+ */
+#define DONT_DROP_OR_WARN __attribute__(unused)
+#endif
+
 /* Specify explicitly a symbol for this function, don't try to guess the c++ mangled symbol.  */
 static nsresult PrepareAndDispatch(nsXPTCStubBase* self, uint32 methodIndex, PRUint32* args) asm("_PrepareAndDispatch")
-__attribute__((used));
+DONT_DROP_OR_WARN;
 
 static nsresult
 PrepareAndDispatch(nsXPTCStubBase* self, uint32 methodIndex, PRUint32* args)