Currently FFTF python script is used for creating flashfiles.zip.
It uses ZipWrite python api which is time consuming and adds
overhead to build time. Say, flash.json generation, unpacking of
target files, installer.cmd generation, etc.

This fix helps to optimize build time and involves below changes:
- Use tar + pigz combo for faster flashfiles generation.
- Make FFTF a bash script as python doesn't directly support
  tar + pigz
- Add use_tar=true flag to "make flashfiles" to enable it.
  e,g, "make flashfiles -j<N> use_tar=true"
- The new script still supports all old functionalities, say,
  generation of installer.cmd, flash.json, repacking of
  bootloader.img, etc.

Tracked-On: OAM-112083
Signed-off-by: sgnanase <[email protected]>
Signed-off-by: Chen, Gang G <[email protected]>

directory is not required in final release packages

Test done:
	make flashfiles use_tar=true
	uzip flashfile.tar.gz and iso.tar.gz, no
	directory in extracted files

Tracked-On: OAM-115260
Signed-off-by: Chen, Gang G <[email protected]>