libjpeg-turbo: don't depend on NASM for non-x86 targets
NASM is a x86-specific assembler so it is only required when building for x86
targets. Use x86-architecture and class-target overrides to depend on NASM, but
explicitly disable and don't depend on it for native as complications in the
native overrides meant NASM was enabled for x86-64 but disabled for x86 (this
will be investigated later).
Original patch by Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>, more
work to solve selftest failures by Richard Purdie
<richard.purdie@linuxfoundation.org>. I just wrote a nice commit message.
Also fix some missing whitespace in _appends.
[ YOCTO #11240 ]
Signed-off-by: Ross Burton <ross.burton@intel.com>
