conftest: macOS: have pyi_builder set up minimal PATH

On macOS, have the `pyi_builder` set up minimal `PATH` before running
the test executable. The minimal `PATH` encompasses system directories
that are also available to applications ran via Finder, a subset
of what is typically available in the shell: `/usr/bin`, `/bin`,
`/usr/sbin`, and `/sbin`.

This accommodates tested python packages that make use of system
utilities - for example, `matplotlib` 3.9.0 started querying system
fonts by running `system_profiler`, which is found in `/usr/sbin`.

PyInstaller/utils/conftest.py

@@ -335,6 +335,12 @@ def _run_executable(self, prog, args, run_from_path, runtime):
         if is_win:
             # Minimum Windows PATH is in most cases:   C:\Windows\system32;C:\Windows
             prog_env['PATH'] = os.pathsep.join(winutils.get_system_path())
+        # On macOS, we similarly set up minimal PATH with system directories, in case utilities from there are used by
+        # tested python code (for example, matplotlib >= 3.9.0 uses `system_profiler` that is found in /usr/sbin).
+        if is_darwin:
+            # The following paths are registered when application is launched via Finder, and are a subset of what is
+            # typically available in the shell.
+            prog_env['PATH'] = os.pathsep.join(['/usr/bin', '/bin', '/usr/sbin', '/sbin'])
 
         exe_path = prog
         if run_from_path: