Avoid bizarre meson behavior with backslashes in command arguments.

Avoid bizarre meson behavior with backslashes in command arguments.

meson makes the backslashes in text2macro.pl's --strip argument
into forward slashes, effectively disabling comment stripping.
That hasn't caused us issues before, but it breaks the test case
for b7e3a52a8.  We don't really need the pattern to be adjustable,
so just hard-wire it into the script instead.

Context: https://github.com/mesonbuild/meson/issues/1564
Security: CVE-2024-10979