python3Packages.pycangjie: fix build with non-default python versions

`find_installation()` without the `name_or_path` argument uses the
Python interpreter that Meson was built with [1], which may not be the
one we're using to build pycangjie.

[1] https://mesonbuild.com/Python-module.html#find_installation

pkgs/development/python-modules/pycangjie/default.nix

@@ -25,6 +25,17 @@ buildPythonPackage rec {
     hash = "sha256-REWX6u3Rc72+e5lIImBwV5uFoBBUTMM5BOfYdKIFL4k=";
   };
 
+  # `find_installation()` without the `name_or_path` argument uses the
+  # Python interpreter that Meson was built with, which may not be the
+  # one we're using to build pycangjie.
+  # https://mesonbuild.com/Python-module.html#find_installation
+  postPatch = ''
+    substituteInPlace meson.build \
+      --replace-fail \
+        "import('python').find_installation()" \
+        "import('python').find_installation('python3')"
+  '';
+
   preConfigure = ''
     (
       cd subprojects