CorebootPayloadPkg: Make shell selectable

CorebootPayloadPkg: Make shell selectable

Add all of the shell options from ShellBinPkg including building the
shell from source.

Enable link time optimization for GCC debug builds to keep the size
under 0x3e0000.

Test: Use -DSHELL_TYPE=BUILD_SHELL command line options to build the
shell from source.  Run the result on Galileo Gen2.

Change-Id: I1e12adb57960ac5e75e682073540a9322aa03081
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-by: Prince Agyeman <prince.agyeman@intel.com>