mkmf.rb: mingw64+MSYS pkg-config fix
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37820 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
mkmf.rb: mingw64+MSYS pkg-config fix
mingw64+MSYS pkg-config which errouneously emits extra newlines.
[ruby-core:47998] [Bug #7163]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37820 b2dd03c8-39d4-4d8f-98ff-823fe69b080e