RFR: 8284772: GHA: Use GCC Major Version Dependencies Only

[Andrew John Hughes]

GHA regularly breaks because we specify a very explicit GCC version, even down to the release versioning of the Ubuntu package.  In just this last week, it has caused issues with the testing of PRs on 11u (https://github.com/openjdk/jdk11u-dev/pull/2084) and 17u (https://github.com/openjdk/jdk17u-dev/pull/1672)

Rather than bumping this yet again like [JDK-8313428](https://bugs.openjdk.org/browse/JDK-8313428), this PR suggests dropping the specific version as we did some time ago in 8u and have now done in 11u (https://github.com/openjdk/jdk11u-dev/pull/2087). The requirement still specifies a specific major version of GCC. It just means the dependency isn't broken every time Ubuntu bumps to a new minor release or even just makes a minor change to the package alone.

Note that the current setup does not guarantee sticking with an exact version of GCC anyway, because - as seen by recent GHA breakage - older versions get removed from the package repository. All we get from this exact version requirement is sporadic breakage of testing and developer time wasted fixing & reviewing (and, in the case of backport trees, approving). If we truly want a static version of GCC, we need to provide our own - or maybe even a full devkit - as we do with the JDK.

-------------

Commit messages:
 - Backport 62defc3dfc4b9ba5adfe3189f34fe8b3f59b94a0

Changes: https://git.openjdk.org/jdk/pull/15374/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15374&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8284772
  Stats: 23 lines in 3 files changed: 0 ins; 18 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/15374.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15374/head:pull/15374

PR: https://git.openjdk.org/jdk/pull/15374