Provide fully-qualified path to shell scripts
Section 3.6.2 of version 2.2 of the shell specification requires that
the first positional argument (i.e. arg 0) of a shell script resolves
to "the full path name of the script itself."
Ensure that the startup script and any scripts launched by the shell
meet this requirement.
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jim Dailey <jim_dailey@dell.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>