ci: add oe-selftest gcc test jobs

gcc test suite has been integrated in oe-selftest framework. It allows
to run gcc test against qemu vm and within the build env using qemu
linux-user mode.

These tests can be run in gitlab CI with qemu friendly runners. This
commit add three oe-selftest jobs to run the tests using qemu
linux-user, qemu x86-64 vm and qemu arm64 vm.

Test log and sum files are collected as job artifacts.

Signed-off-by: Chase Qi <chase.qi@linaro.org>