dependencies: Fix executable file test on Unix.

access(2) tests for X_OK that return true do not always guarantee that
the file is executable.  Instead check the stat(2) mode bits explicitly.

This fixes any builds or installs executed as root on Solaris and
illumos that contain non-executable scripts.

mesonbuild/dependencies/base.py

@@ -21,6 +21,7 @@ import re
 import json
 import shlex
 import shutil
+import stat
 import textwrap
 import platform
 from typing import Any, Dict, List, Optional, Tuple, Type, Union
@@ -1859,10 +1860,11 @@ class ExternalProgram:
 
     def _is_executable(self, path):
         suffix = os.path.splitext(path)[-1].lower()[1:]
+        execmask = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
         if mesonlib.is_windows():
             if suffix in self.windows_exts:
                 return True
-        elif os.access(path, os.X_OK):
+        elif os.stat(path).st_mode & execmask:
             return not os.path.isdir(path)
         return False