exe/ruby: link libm for fiddle test

* common.mk (exe/ruby): $(LIBS) should come after the source file
  due to the ld spec.

* ruby-runner.c (ruby_libm_func): force to link libm for fiddle
  test.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63956 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Author: nobu

common.mk

@@ -834,7 +834,7 @@ $(PLATFORM_D):
 	@exit > $@
 
 exe/$(PROGRAM): ruby-runner.c ruby-runner.h exe/.time miniruby$(EXEEXT)
-	$(Q) $(PURIFY) $(CC) $(CFLAGS) $(CPPFLAGS) -DRUBY_INSTALL_NAME=$(@F) $(LDFLAGS) $(LIBS) $(OUTFLAG)$@ $<
+	$(Q) $(PURIFY) $(CC) $(CFLAGS) $(CPPFLAGS) -DRUBY_INSTALL_NAME=$(@F) $(LDFLAGS) $(OUTFLAG)$@ $< $(LIBS)
 	$(Q) $(POSTLINK)
 	$(Q) ./miniruby$(EXEEXT) \
 	    -e 'prog, dest = ARGV; dest += "/ruby"' \

ruby-runner.c

@@ -43,6 +43,10 @@ insert_env_path(const char *envname, const char *paths, size_t size, int prepend
     setenv(envname, env, 1);
 }
 
+/* force to link libm for fiddle test */
+#include <math.h>
+double (*const ruby_libm_func)(double) = log;
+
 #define EXTOUT_DIR BUILDDIR"/"EXTOUT
 int
 main(int argc, char **argv)