[gitg/wip/chergert/macos-build-fixes] build: remove use of deprecated python3 module

[Christian Hergert <chergert src gnome org>]

commit 22b322c6ac6f9dffc288dd0ec6999f9155520c03
Author: Christian Hergert <christian hergert me>
Date:   Fri Feb 4 15:06:56 2022 -0800

    build: remove use of deprecated python3 module
    
    This can use the non-deprecated python module now that 0.50
    is used for the project.

 libgitg-ext/meson.build | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/libgitg-ext/meson.build b/libgitg-ext/meson.build
index f49c1dbd..0139c0b5 100644
--- a/libgitg-ext/meson.build
+++ b/libgitg-ext/meson.build
@@ -124,10 +124,11 @@ custom_target(
 
 enable_python = get_option('python')
 if enable_python
-  python = import('python3')
+  python = import('python')
+  purelib_path = python.find_installation().get_install_dir()
 
   install_data(
     'GitgExt.py',
-    install_dir: join_paths(python.sysconfig_path('purelib'), 'gi', 'overrides'),
+    install_dir: join_paths(purelib_path, 'gi', 'overrides'),
   )
 endif