RFR: 8283260: gcc is not supported on mac

[Magnus Ihse Bursie]

Nowadays only clang is available as compiler for macOS. We should remove remnants of the gcc support.

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Commit messages:
 - 8283260: gcc is not supported on mac

Changes: https://git.openjdk.java.net/jdk/pull/7841/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7841&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283260
  Stats: 11 lines in 2 files changed: 0 ins; 3 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7841.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7841/head:pull/7841

PR: https://git.openjdk.java.net/jdk/pull/7841