libff: fix enable-shared condition

* ext/fiddle/extconf.rb: needs --enable-shared when linked to
  libruby or fiddle.so.  since --with-static-linked-ext does no
  longer link extensions to ruby program with --enable-shared, the
  only combination needs --enable-static is --disable-shared and
  --with-static-linked-ext.  [ruby-dev:48901] [Bug #10960]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49957 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,11 @@
+Fri Mar 13 11:37:46 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/fiddle/extconf.rb: needs --enable-shared when linked to
+	  libruby or fiddle.so.  since --with-static-linked-ext does no
+	  longer link extensions to ruby program with --enable-shared, the
+	  only combination needs --enable-static is --disable-shared and
+	  --with-static-linked-ext.  [ruby-dev:48901] [Bug #10960]
+
 Fri Mar 13 07:02:20 2015  Eric Wong  <e@80x24.org>
 
 	* ext/socket/init.c (rsock_s_accept_nonblock): use rb_hash_lookup2

ext/fiddle/extconf.rb

@@ -72,7 +72,7 @@ begin
     --host=#{libffi.arch}
     --enable-builddir=#{RUBY_PLATFORM}
   ]
-  args << ($enable_shared && !$static ? '--enable-shared' : '--enable-static')
+  args << ($enable_shared || !$static ? '--enable-shared' : '--enable-static')
   args << libffi.opt if libffi.opt
   args.concat %W[
       CC=#{cc} CFLAGS=#{libffi.cflags}