tests: Undefine _FORTIFY_SOURCE for unit tests to avoid _chk variants

The option _FORTIFY_SOURCE, when enabled, can result in some functions
being expanded into _chk variants. For example, `fprintf` can get
expanded into `__fprintf_chk`. This makes sense for building a real
binary, but is not needed for unit tests.

In unit test environment all those functions are wrapped. In the
example above, both `fprintf` and `__fprintf_chk` needed to be mocked.
Disabling _FORTIFY_SOURCE avoids expanding functions into _chk
variants, without any loss of testing coverage because that would
be wrapped/mocked anyway.

This patch also removes two existing _chk wraps because they are not
needed anymore.

BUG=b:237606255
TEST=ninja test on
1) gcc 12.2.0 on Debian
2) clang 15.0 on Chromium OS

Ticket: https://ticket.coreboot.org/issues/411
Change-Id: I70cb1cd90d1f377ff4606acad3c1b514120ae4f7
Signed-off-by: Anastasia Klimchuk <aklm@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/68432
Reviewed-by: Peter Marheine <pmarheine@chromium.org>
Reviewed-by: Felix Singer <felixsinger@posteo.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

tests/meson.build

@@ -69,9 +69,7 @@ mocks = [
   '-Wl,--wrap=fsync',
   '-Wl,--wrap=fread',
   '-Wl,--wrap=fgets',
-  '-Wl,--wrap=__fgets_chk',
   '-Wl,--wrap=fprintf',
-  '-Wl,--wrap=__vfprintf_chk',
   '-Wl,--wrap=fclose',
   '-Wl,--wrap=feof',
   '-Wl,--wrap=ferror',
@@ -115,6 +113,7 @@ flashrom_tests = executable('flashrom_unit_tests',
     cargs,
     '-ffunction-sections',
     '-fdata-sections',
+    '-U_FORTIFY_SOURCE',
   ],
   export_dynamic : true,
   link_args : mocks,