有人见过这个吗？

Installing json 1.8.6 with native extensions

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    /Users/davidvezzani/.rvm/rubies/ruby-1.9.3-p551/bin/ruby -r ./siteconf20170317-7715-43clev.rb extconf.rb
creating Makefile

make  clean

make
compiling generator.c
make: /usr/local/Cellar/gcc49/4.9.3/bin/gcc-4.9: No such file or directory
make: *** [generator.o] Error 1

make failed, exit code 2

Gem files will remain installed in /Users/davidvezzani/.rvm/gems/ruby-1.9.3-p551/gems/json-1.8.6 for inspection.
Results logged to /Users/davidvezzani/.rvm/gems/ruby-1.9.3-p551/extensions/x86_64-darwin-14/1.9.1/json-1.8.6/gem_make.out

从终端

➜  ~ brew doctor
Your system is ready to brew.

➜  ~ ls /usr/local/Cellar|grep gcc
[email protected]

gcc --version
gcc (Homebrew GCC 4.9.4) 4.9.4
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

看起来我的gcc是4.9.4，而4.9.3被缓存在某个地方。我不知道如何/在哪里清理它。我如何才能最好地解决这个问题？