当它尝试安装json 1.8.3时,我得到以下内容：

Installing json 1.8.3 with native extensions

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

/home/andrew/.rvm/rubies/ruby-2.2.1/bin/ruby -r ./siteconf20150905-31357-cgs3dn.rb extconf.rb
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling generator.c
linking shared-object json/ext/generator.so

make "DESTDIR=" install
./install -m 0755 generator.so ./.gem.20150905-31357-199esvy/json/ext
make: ./install: Command not found
make: *** [install-so] Error 127

make install Failed,exit code 2

在同一台主机上,我可以在ruby 2.1.3中安装json 1.8.3.

在another SO question中,我看到了确保安装可用的建议.当我安装–help时,我得到有效的输出.

我该怎么办？为什么gem能够安装在2.1.3而不是2.2.1中？