[M67 Dev][EFL] Set up build environment

[M67 Dev][EFL] Set up build environment

The gn build is supported by default:
$ ./tizen_src/build/build_desktop.sh

The followings are included in this:

[Build] Use GN by default instead of GYP
https://review.tizen.org/gerrit/#/c/116494/

[Build] Move tizen_src/packaging/ directory to top
https://review.tizen.org/gerrit/#/c/116944/

[A&O] Revise replace_gn_files.py to support multiple replacements
https://review.tizen.org/gerrit/#/c/128811/

fixup! [A&O] Revise replace_gn_files.py to support multiple replacements
https://review.tizen.org/gerrit/#/c/129273/

Upgrade version of efl, elementary
https://review.tizen.org/gerrit/#/c/161190/

Remove the apply_patches.sh calls
https://review.tizen.org/gerrit/#/c/171551/

Change-Id: Id2e9c444434ed7ba5b6557920d111fc802364d71
Signed-off-by: Youngsoo Choi <kenshin.choi@samsung.com>