build: remove unused libatomic and librt on ppc64, s390x
The libraries are not necessary for ppc64 or s390x. It does no harm with some linkers, but devtoolset-6 creates runtime dependencies on all link libraries, even unused ones.
Fixes: https://github.com/nodejs/node/issues/27377 Fixes: https://github.com/nodejs/node/issues/29718
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines