Fix default image base and max page size.
Support more relocation types.
Support secure PLT (see below). musl supports only secure PLT
PowerPC psABI specified an old-style .plt (BSS PLT) (.plt is NOBITS and
written by the dynamic loader) that is both writable and executable.
Linkers don't make separate RW- and RWE segments, which causes all
initially writable memory (think .data) executable. This is a big
security concern so a new PLT scheme (secure PLT) was developed to
address the security issue.
This helps PR40888. Actually, with this patch, I think many
-shared/-static/-pie applications linked against musl will work.
A hello world program linked against glibc doesn't run. TLS is not
implemented but I believe PPC.cpp can just reuse TLS code from
PPC64.cpp. I create ppc32-* instead of ppc-* for tests as I plan to use
ppc-* for tests shareable on ppc32 and ppc64.