Define NDEBUG when building 3rd party libraries.

We are not interested in asserts in 3rd party libraries so make them disappear
by defining NDEBUG when building them.

Closes #11155.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61960 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/regex/regguts.h

@@ -53,8 +53,10 @@
 /* assertions */
 #ifndef assert
 #	ifndef REG_DEBUG
+#	ifndef NDEBUG
 #	define	NDEBUG		/* no assertions */
 #	endif
+#	endif
 #include <assert.h>
 #endif