Fix Windows build on setuptools that default to local distutils.

This is a cross port of
matplotlib/mplcairo@2991c72 and
matplotlib/mplcairo@2991c72

Fixes matplotlib#23147

Co-authored-by: Antony Lee <[email protected]>

Author: QuLogic

setupext.py

@@ -12,6 +12,7 @@
 import sys
 import sysconfig
 import tarfile
+from tempfile import TemporaryDirectory
 import textwrap
 import urllib.request
 
@@ -691,15 +692,31 @@ def do_custom_build(self, env):
                 f.write(vcxproj)
 
             cc = get_ccompiler()
-            cc.initialize()  # Get msbuild in the %PATH% of cc.spawn.
+            cc.initialize()
+            # On setuptools versions that use "local" distutils,
+            # ``cc.spawn(["msbuild", ...])`` no longer manages to locate the
+            # right executable, even though they are correctly on the PATH,
+            # because only the env kwarg to Popen() is updated, and not
+            # os.environ["PATH"]. Instead, use shutil.which to walk the PATH
+            # and get absolute executable paths.
+            with TemporaryDirectory() as tmpdir:
+                dest = Path(tmpdir, "path")
+                cc.spawn([
+                    sys.executable, "-c",
+                    "import pathlib, shutil, sys\n"
+                    "dest = pathlib.Path(sys.argv[1])\n"
+                    "dest.write_text(shutil.which('msbuild'))\n",
+                    str(dest),
+                ])
+                msbuild_path = dest.read_text()
             # Freetype 2.10.0+ support static builds.
             msbuild_config = (
                 "Release Static"
                 if [*map(int, LOCAL_FREETYPE_VERSION.split("."))] >= [2, 10]
                 else "Release"
             )
 
-            cc.spawn(["msbuild", str(sln_path),
+            cc.spawn([msbuild_path, str(sln_path),
                       "/t:Clean;Build",
                       f"/p:Configuration={msbuild_config};"
                       f"Platform={msbuild_platform}"])