build-unit-test-docker: update to gcc-13

Yocto upstream is now on GCC-13, which we will be merging as soon as all
code compiles successfully.  Update the docker container for CI as well
so we do not get any regressions.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I8bab7fb5acfe0d19d03729a69d8cacac7e571b5b
1 file changed