meson: windows: Fix tmp_install + prefix computation with meson 1.0.1

In d0366bfb3b21 I said:
    Instead of trying to do this in meson.build, call out to the implementation
    meson install uses. This isn't pretty, but it's more reliable than what we had
    before.

Unfortunately it was too ugly - to fix a bug, meson 1.0.1 changed the way the
meson internal runpython helper works, resulting in the previous sys.argv[]
indices not working anymore.  Just open-code it - it's just a few characters
longer.

Committing this quickly to allow ci/cfbot to work with meson 1.0.1 on windows.

diff --git a/meson.build b/meson.build
index f5347044526734a3669c45e55dda8558e4af5a3e..656777820c8d0aced4e459ac775802e208c337d8 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -2880,10 +2880,10 @@ if build_system != 'windows'
   test_install_location = '@0@@1@'.format(test_install_destdir, dir_prefix)
 else
   # drives, drive-relative paths, etc make this complicated on windows, call
-  # meson's logic for it
+  # into a copy of meson's logic for it
   command = [
-    meson_bin, meson_args, 'runpython', '-c',
-    'import sys; from mesonbuild.scripts import destdir_join; print(destdir_join(sys.argv[4], sys.argv[5]))',
+    python, '-c',
+    'import sys; from pathlib import PurePath; d1=sys.argv[1]; d2=sys.argv[2]; print(str(PurePath(d1, *PurePath(d2).parts[1:])))',
     test_install_destdir, dir_prefix]
   test_install_location = run_command(command, check: true).stdout().strip()
 endif