Apply Dredd to GCC

[afd]

The GCC project doesn't use CMake - it uses an older auto-tools-based build system. This does not support generating a compilation database, so we will need to use a build system interceptor, such as bear, to get the compile commands.

Rough steps for this:

• Work out how to build regular GCC
• Work out how to use bear (or equivalent tool) to extract a compilation database
• Confirm that this then enables running Dredd
• Confirm that GCC then still compiles and that tests execute successfully
• Other members of the multicore group have experience building GCC, which we can draw on.