oeqa/selftest/cases/gcc.py: Split into classes for parallelism
Split the gcc selftest cases into multiple classes one for each test.
This is done in order to make it easy to execute multiple gcc tests in
parallel when using oe-selftest with the '-j' arg.
Additionally tag the user tests with "toolchain-user" and the system
emulation (qemu system) tests with "toolchain-system".
Signed-off-by: Nathan Rossi <nathan@nathanrossi.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
