[crac] RFR: GLIBC->CPU flags optimization

[Jan Kratochvil]

Reduce the number of `GLIBC_*` flags when it can use existing `CPU_*` flags.
This patch was split out of PR #136.

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Commit messages:
 - GLIBC->CPU flags optimization

Changes: https://git.openjdk.org/crac/pull/139/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=139&range=00
  Stats: 19 lines in 2 files changed: 2 ins; 10 del; 7 mod
  Patch: https://git.openjdk.org/crac/pull/139.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/139/head:pull/139

PR: https://git.openjdk.org/crac/pull/139