ci: Suppress hanging CMakeGUI test on macos-x86_64 jobs

This test has been spuriously hanging in macos-x86_64 CI jobs since
our update to Qt 6.9.3.  Suppress it pending further investigation.

Issue: #27376

.gitlab/ci/ctest_exclusions.cmake

@@ -48,6 +48,13 @@ if ("$ENV{CMAKE_CONFIGURATION}" MATCHES "_xcode")
     )
 endif()
 
+if ("$ENV{CMAKE_CONFIGURATION}" MATCHES "^macos_x86_64_")
+  list(APPEND test_exclusions
+    # FIXME(#27376): CMakeGUI's simpleConfigure:fail case hangs.
+    "^CMakeGUI$"
+    )
+endif()
+
 string(REPLACE ";" "|" test_exclusions "${test_exclusions}")
 if (test_exclusions)
   set(test_exclusions "(${test_exclusions})")