Clean up GCC build.

Make the Unix Vlv2TbltDevicePkg scripts executable, add shebangs and skip the requirement to press a key when displaying usage text from Build_IFWI.sh.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Bruce Cran <bruce.cran@gmail.com>
Reviewed-by: David Wei <david.wei@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16936 6f19259b-4bc3-4df7-8a09-765794883524