Hardcode executable path so that the symlink in the standard PATH
works correctly.

--- jruby-launcher/jrubyexe.cpp.orig	Fri Dec  2 09:34:43 2011
+++ jruby-launcher/jrubyexe.cpp	Fri Dec  2 09:35:02 2011
@@ -57,8 +57,10 @@ const char *CON_ATTACH_MSG =
 
 #include "utilsfuncs.h"
 
+char JRUBY_PATH[] = "${PREFIX}/jruby/bin/jruby";
 
 int main(int argc, char *argv[], char* envp[]) {
+    argv[0] = JRUBY_PATH;
     checkLoggingArg(argc, argv, true);
 
 #ifdef WIN32