tests: posix: c_lib_ext: Disable failing tests when using our fnmatch

Zephyr fnmatch() fails couple of newly added tests so disable them
if using our own version.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>

Author: jukkar

tests/posix/c_lib_ext/src/fnmatch.c

@@ -83,9 +83,14 @@ ZTEST(posix_c_lib_ext, test_fnmatch)
 	zassert_equal(fnmatch("*/*", "a/.b", FNM_PATHNAME | FNM_PERIOD), FNM_NOMATCH);
 	zassert_ok(fnmatch("*?*/*", "a/.b", FNM_PERIOD));
 	zassert_ok(fnmatch("*[.]/b", "a./b", FNM_PATHNAME | FNM_PERIOD));
-	zassert_ok(fnmatch("*[[:alpha:]]/""*[[:alnum:]]", "a/b", FNM_PATHNAME));
-	zassert_ok(fnmatch("*[![:digit:]]*/[![:d-d]", "a/b", FNM_PATHNAME));
-	zassert_ok(fnmatch("*[![:digit:]]*/[[:d-d]", "a/[", FNM_PATHNAME));
+
+	/* Disable tests that fail when using Zephyr's fnmatch implementation */
+	if (!IS_ENABLED(CONFIG_POSIX_C_LIB_EXT)) {
+		zassert_ok(fnmatch("*[[:alpha:]]/""*[[:alnum:]]", "a/b", FNM_PATHNAME));
+		zassert_ok(fnmatch("*[![:digit:]]*/[![:d-d]", "a/b", FNM_PATHNAME));
+		zassert_ok(fnmatch("*[![:digit:]]*/[[:d-d]", "a/[", FNM_PATHNAME));
+	}
+
 	zassert_not_equal(fnmatch("*[![:digit:]]*/[![:d-d]", "a/[", FNM_PATHNAME), 0);
 	zassert_ok(fnmatch("a?b", "a.b", FNM_PATHNAME | FNM_PERIOD));
 	zassert_ok(fnmatch("a*b", "a.b", FNM_PATHNAME | FNM_PERIOD));