meson: Strip quotes from BR2_ENDIAN

meson: Strip quotes from BR2_ENDIAN

The values in the cross-compilation file are expected to be quoted with
single quotes, which we have in our template.

However, the endian value we are injecting comes from Kconfig, so it is
double-quoted, and those quotes end up in the cross-compilation files we
generate (the internal one, and the SDK one):

    endian = '"little"'

So qstrip the value before we inject it.

Propagate the fix to the two generated files by using the same variable
HOST_MESON_TARGET_ENDIAN in both cases, rather than replicating the
(flawed) logic.

While at it, also use the common GCC_TARGET_CPU variable for the SDK
file too.

Signed-off-by: Gleb Mazovetskiy <glex.spb@gmail.com>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>