nasm: disable LTO, remove host specific workarounds

The recent build failures on various platforms were apparently caused by
the fact that LTO build support in the configure script does not check
if it has a suitable version of gcc and simply assumes that gcc-ar is
available and can be used for intermediate files.

Since we really don't need to build nasm with LTO, simply disable it and
keep the whole build more portable

Signed-off-by: Felix Fietkau <nbd@nbd.name>