phantomjs2: don't use bundled qt

pkgs/development/tools/phantomjs2/system-qtbase.patch

@@ -0,0 +1,13 @@
+--- a/build.py
++++ b/build.py
+@@ -80,9 +80,9 @@
+ def qmakePath():
+     exe = "qmake"
+     if platform.system() == "Windows":
+         exe += ".exe"
+-    return os.path.abspath("src/qt/qtbase/bin/" + exe)
++    return os.path.abspath("@qtbase@" + exe)
+ 
+ # returns paths for 3rd party libraries (Windows only)
+ def findThirdPartyDeps():
+     include_dirs = []