oeqa/selftest/minidebuginfo: Create selftest for minidebuginfo

Add a new selftest to validate minidebuginfo support. This selftest
builds a complete target image with PACKAGE_MINIDEBUGINFO enabled. ELFs
included in the image are expected to have minidebuginfo included in the
resulting executables and shared libraries, the self test validates this
by unpacking the image and checking for the associated ".gnu_debugdata"
section on busybox and libc ELFs.

Signed-off-by: Nathan Rossi <nathan.rossi@digi.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>