Use the official docker image of GCC compilers for CI jobs

[fktn-k]

Currently, CI jobs to check build results with GCC compilers are achieved by using a self-hosted runner which preinstalls various versions of GCC compilers.
However, it would cost a lot to maintain those versions up to date.
To make it at least simpler than it is, I want to change the way of using GCC compilers into the one which depends on the official docker image for them.

[fktn-k]

Completed in #110