osdep: Create qemu_getauxval and qemu_init_auxval

Abstract away dependence on a system implementation of getauxval.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-ppc64: Use qemu_getauxval

Allow host detection on linux systems without glibc 2.16 or later.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-arm: Use qemu_getauxval

Allow host detection on linux systems without glibc 2.16 or later.

Signed-off-by: Richard Henderson <rth@twiddle.net>
tcg-s390: Use qemu_getauxval in query_facilities

No need to set up a SIGILL signal handler for detection anymore.

Remove a ton of sanity checks that must be true, given that we're
requiring a 64-bit build (the note about 31-bit KVM is satisfied
by configuring with TCI).

Signed-off-by: Richard Henderson <rth@twiddle.net>
util: Provide fallback hwcap and platform for powerpc

Allow host "detection" on non-linux hosts.

Signed-off-by: Richard Henderson <rth@twiddle.net>
util: Use qemu_getauxval in linux qemu_cache_utils_init

With this we no longer pass down envp, and thus all systems can have
the same void prototype.  So also eliminate a useless thunk.

Signed-off-by: Richard Henderson <rth@twiddle.net>
linux-user: Use qemu_getauxval for AT_EXECFD

Signed-off-by: Richard Henderson <rth@twiddle.net>