qt: set CC/CXX correctly

Library/Formula/qt.rb

@@ -28,6 +28,11 @@ class Qt < Formula
     sha256 "b5001ee9df42d77d22b32624c80af37205be4783a964ccfe26f4f754ee7a2dbe"
   end
 
+  patch :p0 do
+    url "https://raw.githubusercontent.com/macports/macports-ports/master/aqua/qt4-mac/files/patch-mkspecs_common_g%2B%2B-base.conf.diff"
+    sha256 "cd023a7a300d9d2a993e707e0374fb944a45e49fe8e50834b157ee330c9901f0"
+  end
+
   patch :p0 do
     url "https://raw.githubusercontent.com/macports/macports-ports/master/aqua/qt4-mac/files/patch-mkspecs_common_g++-macx.conf.diff"
     sha256 "e356c4cac6675bd6c2e6886ccbbcb3c4fde5ef7b643446d6239712e3606b6767"
@@ -118,6 +123,11 @@ class Qt < Formula
       s.gsub! "@ARCHES@", arch.to_s
     end
 
+    inreplace "mkspecs/common/g++-base.conf" do |s|
+      s.gsub! "@CC@", ENV.cc
+      s.gsub! "@CXX@", ENV.cxx
+    end
+
     args = ["-prefix", prefix,
             "-system-zlib",
             "-qt-libtiff", "-qt-libpng", "-qt-libjpeg",