With v250 systemd-boot gained support for LTO builds (which already works for the current build in testing). But it could benefit even more if gnu-efi was built with LTO too…

Additionally, while looking at the PKGBUILD, I noticed that we currently pass our userspace CFLAGS as-is to make. I consider this a bad idea for gnu-efi as it's not your typical userspace program. It's a freestanding compilation and as such, the compile flags should be heavily restricted. One example that could easily break things is '-march=x86_64-v3': This would allow the compiler to use instructions that may not be available *yet* at the time the boot loader runs because they might need to be enabled explicitly or because the firmware APIs that are called aren't prepared to save relevant CPU states.

As such, I would strongly suggest to only use these CFLAGS in PKGBUILD and let gnu-efi decide on anything else it wants:
export CFLAGS="-O2 -flto -ffat-lto-objects"