support/testing: add suite of tests for gdb

The list of tests is as follows:

TestGdbHostOnlyDefault: build just minimal host-gdb, default version

TestGdbHostOnlyAllFeatures: build host-gdb, default version, with all
features enabled (TUI, Python, simulator)

TestGdbserverOnly: build just target gdbserver, default version

TestGdbFullTarget: build just target gdb, default version

TestGdbHostOnly9x: build minimal host-gdb, 9.x version

TestGdbHostGdbserver9x: build minimal host-gdb 9.x + gdbserver

TestGdbHostGdbTarget9x: build minimal host-gdb 9.x + full gdb

TestGdbHostOnly11x: build minimal host-gdb, 11.x version

TestGdbHostGdbserver11x: build minimal host-gdb 11.x + gdbserver

TestGdbHostGdbTarget11x: build minimal host-gdb 11.x + gdb

TestGdbArc: build minimal host-gdb + gdb + gdbserver, for the special
ARC architecture version

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>