error.c: export rb_assert_failure

to test JIT with `VM_CHECK_MODE=1`

It's failing on CI which enables VM_CHECK_MODE.

:   1)
: TestJIT#test_jit [/home/ko1/ruby/src/trunk-vm-asserts/test/ruby/test_jit.rb:10]:
: Expected 1 times of JIT success, but succeeded 0 times.
:   2)
: TestJIT#test_jit_output [/home/ko1/ruby/src/trunk-vm-asserts/test/ruby/test_jit.rb:18]:
: Expected /^JIT success \(\d+\.\dms\): block in <main>@-e:1 -> .+_ruby_mjit_p\d+u\d+\.c$/ to match "MJIT warning: failure in loading code from '/tmp/_ruby_mjit_p9896u0.so': /tmp/_ruby_mjit

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62296 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

error.c

@@ -660,7 +660,7 @@ rb_report_bug_valist(VALUE file, int line, const char *fmt, va_list args)
     report_bug_valist(RSTRING_PTR(file), line, fmt, NULL, args);
 }
 
-void
+MJIT_FUNC_EXPORTED void
 rb_assert_failure(const char *file, int line, const char *name, const char *expr)
 {
     FILE *out = stderr;