Build History for branch/endbr64

bti: do not emit BTI instructions unless configured Depending on the presence of cet.h will end up emitting them on most modern compilers, so this specifically checks for the --enable-bti flag being pass to configure

bti: enable automatically on openbsd/x86_64 This also obeys an explicit directive for the configure flag if specified. So --enable-bti will always attempt to compile with BTI, and --disable-bti will always disable it (even if required on the platform). Not specifying the flag will cause the configure script to try and do the right thing.