[3.13] gh-126554: correct detection of gcc for TestNullDlsym.test_null_dlsym (GH-129872) (#129944)

gh-126554: correct detection of `gcc` for `TestNullDlsym.test_null_dlsym` (GH-129872)

In case gcc is not available, the test will fail with FileNotFoundError.
So catch the exception to skip the test correctly.
(cherry picked from commit 978211c)

Signed-off-by: Peter Marko <peter.marko@siemens.com>
Co-authored-by: Peter Marko <peter.marko@siemens.com>

Author: miss-islington

Lib/test/test_ctypes/test_dlerror.py

@@ -58,11 +58,14 @@ def test_null_dlsym(self):
         import subprocess
         import tempfile
 
-        retcode = subprocess.call(["gcc", "--version"],
-                                  stdout=subprocess.DEVNULL,
-                                  stderr=subprocess.DEVNULL)
-        if retcode != 0:
+        try:
+            retcode = subprocess.call(["gcc", "--version"],
+                                      stdout=subprocess.DEVNULL,
+                                      stderr=subprocess.DEVNULL)
+        except OSError:
             self.skipTest("gcc is missing")
+        if retcode != 0:
+            self.skipTest("gcc --version failed")
 
         pipe_r, pipe_w = os.pipe()
         self.addCleanup(os.close, pipe_r)