build(vim-patch): v9.0.1557 is n/a

Global variables with "_for_testing" suffix are modified
in "f_test_override()", N/A to Nvim.
If a test needs them, then port the relevant code outside
"f_test_override()" via LuaJIT C FFI.

scripts/vim-patch.sh

@@ -997,7 +997,7 @@ is_na_patch() {
           '-I^\s+(CH_MODE|POPCLOSE)_[A-Z]+,?$' \
           '-I^\} popclose_T;$' \
           '-I^EXTERN\schar\s+\*popup_transparent' \
-          '-I^EXTERN\sint\s+disable_vterm_title_for_testing' \
+          '-I^EXTERN\sint\s+[_a-z]+_for_testing\s' \
           '-I^EXTERN type_T static_types\[' \
           '-I^EXTERN type_T t_.* INIT[2-9]\(' \
           '-I^EXTERN\swin_T\s+\*popup_dragwin' \