Fix two scan-build warnings that appear on F41

Fix two scan-build warnings that appear on F41

../../../src/util-files.h:61:3: warning: The 1st argument to 'close' is <= -2 but should be >= -1 [unix.StdCLibraryFunctions]
   61 |                 close(*fd);

 ../../../test/test-quirks.c:66:8: warning: Null pointer passed to 2nd parameter expecting 'nonnull' [core.NonNullParamChecker]
   66 |                 rc = fputs(file_content, fp);

The latter is bogus because we have a litest_assert for this but
somehow this is ignored, so... shrug.

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1111>