I'm currently working on building Guix System for powerpc64le, and I've
encountered a few issues that I could use some assistance with.

Firstly, linux-initrd failing because gcc-7.5 package used for
bootstrap-glibc do not support --with-long-double-128. Removing this works
just fine -- with last gcc package:
> /gnu/packages/make-bootstrap.scm
> (native-inputs
>     `(("gcc" ,gcc-7.5)
>         ,@(package-native-inputs base)))

I'm curious why gcc-7.5 was built without --with-long-double-128,
especially considering it's defined for powerpc64le-linux in
/gnu/packages/gcc.scm under (gcc-configure-flags-for-triplet).

Furthermore, I've encountered issues with Grub, which are detailed in this
issue: https://issues.guix.gnu.org/54407. I believe that porting
gcc-12-multilib from Debian could potentially resolve this problem.

Lastly, any image generated from (system-disk-image) depends on
grub-efi{,32}, but (a) grub-efi build fails on ppc*, and (b) ppc* systems
do not use EFI.

The remaining problems mostly involve software patching or minor code
adjustments.

Best regards,

Mykhailo Chernysh
iskrim666@gmail.com