util/abuild: Fix or disable shellcheck warnings

This cleans up the shellcheck warnings in abuild.

Warning count:
1 Unexpected ==.
1 Use "${var:?}" to ensure this never expands to / .
1 VARIABLE appears unused. Verify it or export it.
1 Use "$@" (with quotes) to prevent whitespace problems.
2 Consider using { cmd1; cmd2; } >> file instead of individual redirects.
2 Expressions don't expand in single quotes, use double quotes for that.
3 Prefer [ p ] || [ q ] as [ p -o q ] is not well defined.
4 $/${} is unnecessary on arithmetic variables.
5 Check exit code directly with 'if mycmd;', not indirectly with $?.
5 Use cd ... || exit in case cd fails.
11 Declare and assign separately to avoid masking return values.
13 Use $(..) instead of legacy `..`.
20 Don't use variables in the printf format string.
104 Double quote to prevent globbing.

Change-Id: I9c77e122435ba87ce3a4aee76b5022f7265f9ef2
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/17722
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
1 file changed