merge revision(s) 54999: [Backport #12379]
* lib/mkmf.rb (pkg_config): use xsystem consistently to set up library path environment variable as well as latter pkg-config calls. [ruby-dev:49619] [Bug #12379]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@55001 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 54999: [Backport #12379]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@55001 b2dd03c8-39d4-4d8f-98ff-823fe69b080e