libebl: Handle aarch64 bti, pac bits in gnu property note

When building with gcc -mbranch-protection= we might get a gnu property
note indicating BTI (Branch Target Identification) and/or PAC (Pointer
Authentication Code) is being used.

Add a small testcase to show eu-readelf -n now properly lists those
bits in the gnu property note.

Signed-off-by: Mark Wielaard <mark@klomp.org>
6 files changed