pc-bios: ensure installed ROMs don't have execute permissions

pc-bios: ensure installed ROMs don't have execute permissions

We have been inconsistent about whether ROMS stored in git have
execute permission set, and by default meson will preserve source
file permissions when installing files. This has caused periodic
problems in RPM packaging as executable binary files get analysed
by various tools/linters, which can trip up on the ROMs.

Tell meson explicitly that all the ROMs should be without execute
permission when installed.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Helge Deller <deller@gmx.de>
Tested-by: Helge Deller <deller@gmx.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250530152118.65030-1-berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>