Stop passing CC_LIBS in compile_c_to_o

To fix "gcc: -lgcc: linker input file unused because linking not done" in
https://rubyci.org/logs/rubyci.s3.amazonaws.com/openbsd65/ruby-master/log/20190826T200009Z.log.html.gz

Still I'm intentionally leaving CC_DLDFLAGS_ARGS because making compiler
options different might result in compile/link failure. (Of course
CC_DLDFLAGS_ARGS usually should not have compiler options, but it might
include by bad configure setup)

The same problem may exist in MJIT_LIBS used inside CC_LIBS as well, but
I just ignored that case because it impacts only MinGW / cygwin, hoping
that their users do not perform a wrong configure.

mjit_worker.c

@@ -792,7 +792,7 @@ compile_c_to_o(const char *c_file, const char *o_file)
         "-c", NULL
     };
 
-    char **args = form_args(5, cc_common_args, CC_CODEFLAG_ARGS, files, CC_LIBS, CC_DLDFLAGS_ARGS);
+    char **args = form_args(4, cc_common_args, CC_CODEFLAG_ARGS, files, CC_DLDFLAGS_ARGS);
     if (args == NULL)
         return false;