vk-gl-cts: allow the user to specify the target
vk-gl-cts: allow the user to specify the target

When building opengl-es-cts (for example), instead of hard-coding a
specific target to build (surfaceless), leave the choice empty by default
which instructs the package's build system to search the sysroot and try to
determine which target to use (i.e. the "Default" target).

Provide overrides (in the form of PACAKGECONFIGs) to allow the user to
specify a specific target to build (if they don't want the target selected
automatically).

Signed-off-by: Trevor Woerner <8835777cd84fba3d7873eabbbe1f2de2d3f25b00@gmail.com>
Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

moto-timo/meta-openembedded,openembedded/meta-openembedded,openembedded/meta-openembedded,openembedded/meta-openembedded,openembedded/meta-openembedded,openembedded/meta-openembedded,schnitzeltony/meta-openembedded,moto-timo/meta-openembedded,moto-timo/meta-openembedded,openembedded/meta-openembedded,rehsack/meta-openembedded,schnitzeltony/meta-openembedded,schnitzeltony/meta-openembedded,moto-timo/meta-openembedded,rehsack/meta-openembedded,rehsack/meta-openembedded,schnitzeltony/meta-openembedded,schnitzeltony/meta-openembedded,schnitzeltony/meta-openembedded,moto-timo/meta-openembedded,rehsack/meta-openembedded,openembedded/meta-openembedded,rehsack/meta-openembedded,openembedded/meta-openembedded,schnitzeltony/meta-openembedded,rehsack/meta-openembedded,rehsack/meta-openembedded