Build - fix bash completion sourcing

Sourcing functions in files from a function within a file being
sourced was giving bash a hard time. This fixes 'repo' command tab
completions.

Change-Id: Ic759dcc4d815adb97727c41d4937299bc2b7bdb1
Signed-off-by: STELIX <ssspinni@gmail.com>
Build - Fix file-size stats on OSX

Kernel makefiles that the stat on the system is GNU stat. GNU stat uses
the "-c" option to specify format.
Darwin stat uses the "-f" option to specify format. This discrepency
will cause kernel build breaks.
On my system, I symlink stat to GNU stat. This causes the "get-file-
size" define
to fail.
The fix for this is to detect "gstat", aka GNU stat, and use that
appropriately.

Fix up the get-file-size function that was broken due to the prior
commit that made it utilize gnu stat (gstat)

Change-Id: I4a8e9cc9ccb91729893d196c54d7e01b46f82fad
Signed-off-by: STELIX <ssspinni@gmail.com>