Switch from mips to powerpc for cross target #378

Job	Run time
feature_check	1m 6s
build (1.57.0, ubuntu-latest)	3m 13s
powerpc_cross	13s
feature_check (benchmarks)	1m 5s
rustfmt	16s
build (1.57.0, windows-latest)	4m 21s
build (1.57.0, macos-latest)	5m 27s
test_all	1m 17s
build (stable, ubuntu-latest)	8s
build (stable, windows-latest)	42s
build (stable, macos-latest)	24s
build (beta, ubuntu-latest)	14s
build (beta, windows-latest)	52s
build (beta, macos-latest)	26s
build (nightly, ubuntu-latest)	16s
build (nightly, windows-latest)	51s
build (nightly, macos-latest)	23s
	21m 14s

Provide feedback