Revert "guix: temporarily disable powerpcle taget"

This reverts commit 10d5653 (bitcoin#27897)

Author: luke-jr

contrib/guix/guix-build

@@ -74,8 +74,7 @@ mkdir -p "$VERSION_BASE"
 ################
 
 # Default to building for all supported HOSTs (overridable by environment)
-# powerpc64le-linux-gnu currently disabled due non-determinism issues across build arches.
-export HOSTS="${HOSTS:-x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv64-linux-gnu powerpc64-linux-gnu
+export HOSTS="${HOSTS:-x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv64-linux-gnu powerpc64-linux-gnu powerpc64le-linux-gnu
                        x86_64-w64-mingw32
                        x86_64-apple-darwin arm64-apple-darwin}"