toolchain/gcc: Backport patch to fix unconditional MULTIARCH_DIRNAME
This backports the patch for GCC PR target/89587 (gcc's rs6000
configuration unconditionally sets MULTIARCH_DIRNAME, even when
multiarch is disabled).
This currently affects apm821xx and may cause issues when
cross-compiling packages, e.g. Python 3.
This includes patches for GCC 8 (with the changelog diff removed);
this change is already included in GCC 9.2 and 7.5.
Signed-off-by: Jeffery To <email@example.com>
[Removed patch for GCC 7.4.0, GCC 7.5.0 already contains this]
Signed-off-by: Hauke Mehrtens <firstname.lastname@example.org>