ports built with gcc instead of clang will fail to start with a fatal error:

Fatal Error: Mismatch between the program and library build versions detected.
The library used 3.0 (wchar_t,compiler with C++ ABI 1002,wx containers,compatible with 2.6,compatible with 2.8),
and your program used 3.0 (wchar_t,compiler with C++ ABI 1009,wx containers,compatible with 2.6,compatible with 2.8).
Abort (core dumped)

This patch changes the fatal error to a warning to allow the programs to still function.

root@upstairs:/usr/ports/x11-toolkits/wxgtk30 # svn diff
Index: files/patch-src-common-appbase.cpp
===================================================================
--- files/patch-src-common-appbase.cpp  (nonexistent)
+++ files/patch-src-common-appbase.cpp  (working copy)
@@ -0,0 +1,15 @@
+--- src/common/appbase.cpp.orig        2014-10-06 14:33:44.000000000 -0700
++++ src/common/appbase.cpp     2017-06-05 21:16:18.988544000 -0700
+@@ -762,10 +762,10 @@
+         msg.Printf(wxT("Mismatch between the program and library build versions detected.\nThe library used %s,\nand %s used %s."),
+                    lib.c_str(), progName.c_str(), prog.c_str());
+ 
+-        wxLogFatalError(msg.c_str());
++        wxLogWarning(msg.c_str());
+ 
+         // normally wxLogFatalError doesn't return
+-        return false;
++        //return false;
+     }
+ 
+     return true;