configure.in: use the first candidate

* configure.in (ac_cv_func___builtin_setjmp): use the first cast
  which works with __builtin_longjmp().  [Bug #9692]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45509 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.in

@@ -2089,7 +2089,7 @@ RUBY_WERROR_FLAG(
     void (*volatile f)(void) = t;
     if (!__builtin_setjmp($cast jb)) printf("%d\n", f != 0);
     ],
-    [ac_cv_func___builtin_setjmp="yes with cast ($cast)"],
+    [ac_cv_func___builtin_setjmp="yes with cast ($cast)"; break],
     [ac_cv_func___builtin_setjmp=no])
 ])
 done])