treewide: Remove uses of builtins.toPath.

toPath has confusing semantics and is never necessary; it can always
either just be omitted or replaced by pre-concatenating `/.`. It has
been marked as "!!! obsolete?" for more than 10 years in a C++
comment, hopefully removing it will let us properly deprecate and,
eventually, remove it.

pkgs/development/mobile/androidenv/androidndk.nix

@@ -50,7 +50,7 @@ stdenv.mkDerivation rec {
 
           patch -p1 \
             --no-backup-if-mismatch \
-            -d $out/libexec/${name} < ${ ./. + builtins.toPath ("/make_standalone_toolchain.py_" + "${version}" + ".patch") }
+            -d $out/libexec/${name} < ${ ./. + "/make_standalone_toolchain.py_${version}.patch" }
           wrapProgram ${pkg_path}/build/tools/make_standalone_toolchain.py --prefix PATH : "${runtime_paths}"
         ''
     }