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.

When all test jobs finish, report job will be triggered to parse the
sum files to generate results in the format that supported by squad. The
report job will upload results to squad for reporting.

Closes issues #8 and #9.

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