RFR: 8293098: GHA: Harmonize GCC version handling for host and cross builds [v2]

[Aleksey Shipilev]

> Caught this headache while trying to bump to Ubuntu 22.04, which required touching way too many surprising places. 
> 
> Current GHA scripts define `apt-gcc-version` a bit weirdly: host and cross builds version differ in carrying the "gcc-major-version" inside of it. That is, "host" builds do `apt-gcc-version: '10=10.3.0-1ubuntu1~20.04'`, while cross builds do `apt-gcc-version: default: '10.3.0-1ubuntu1~20.04'`
> 
> I propose we harmonize these to simplify GCC updates: split out the `gcc-major-version` for host builds, and pull the versions from cross builds into `main`, where all other versions belong. Additionally, this handles the x86_32 case that requires "-multilib" package, which is currently hacked through the "version" string.
> 
> Additional testing:
>  - [ ] GHA

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Allow cross-compiler to have slightly different version

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10083/files
  - new: https://git.openjdk.org/jdk/pull/10083/files/8205aeb3..2074c729

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10083&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10083&range=00-01

  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/10083.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10083/head:pull/10083

PR: https://git.openjdk.org/jdk/pull/10083