[build] Mark compressed image tools as permitted for UEFI Secure Boot

[build] Mark compressed image tools as permitted for UEFI Secure Boot

Some older distributions (such as RHEL 8) provide their AArch64
kernels as gzip-compressed EFI binaries (with no self-decompressing
EFI stub present).  We therefore enable support for gzip images by
default for arm64 EFI builds.

Review the files used to implement the gzip (and zlib) formats and
mark these as permitted for UEFI Secure Boot.

Signed-off-by: Michael Brown <mcb30@ipxe.org>