python3Packages.pyqt-builder: use sip-distinfo from PATH

Fixes PyQt5 build.

pkgs/development/python-modules/pyqt-builder/default.nix

···
     sha256 = "sha256-SHdYDDjOtTIOEps4HQg7CoYBxoFm2LmXB/CPoKFonu8=";
   };
 
+  patches = [
+    # use the sip-distinfo executable from PATH instead of trying to guess,
+    # we know it's the right one because it's the _only_ one
+    ./use-sip-distinfo-from-path.patch
+  ];
+
   propagatedBuildInputs = [ packaging sip ];
 
   pythonImportsCheck = [ "pyqtbuild" ];

pkgs/development/python-modules/pyqt-builder/use-sip-distinfo-from-path.patch

···
+diff --git a/pyqtbuild/builder.py b/pyqtbuild/builder.py
+index 3f35a7f..58701dd 100644
+--- a/pyqtbuild/builder.py
++++ b/pyqtbuild/builder.py
+@@ -51,15 +51,6 @@ class QmakeBuilder(Builder):
+         """ Set default values for user options that haven't been set yet. """
+ 
+         if tool in Option.BUILD_TOOLS:
+-            # A PEP 517 frontend will set PATH so that sip-distinfo is found on
+-            # it.  However for our own frontends we want to use the version
+-            # corresponding to the frontend (and, anyway, the frontend may not
+-            # be on PATH).
+-            if tool != 'pep517':
+-                self._sip_distinfo = os.path.join(
+-                        os.path.abspath(os.path.dirname(sys.argv[0])),
+-                        self._sip_distinfo)
+-
+             # Check we have a qmake.
+             if self.qmake is None:
+                 self.qmake = self._find_exe('qmake')