lbmk: don't use status for unconditional returns

in cases where lbmk must always return from a function,
there are some cases where it relies on non-zero exit
status, which in practise is always the case, but may
change in the future if the relevant part is modified

e.g. do_something && return 0

the proper form is:
do_something
return 0

also do this for unconditional exits

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/update/trees

@@ -37,8 +37,11 @@ main()
 	[ -z "${_f}" ] && err "missing flag (-m/-u/-b/-c/-x/-f/-s/-l/-n)"
 	[ -z "${project}" ] && err "project name not specified"
 
-	[ -f "config/${project}/build.list" ] && build_targets $@ && return 0
-	build_projects $@
+	if [ -f "config/${project}/build.list" ]; then
+		build_targets $@
+	else
+		build_projects $@
+	fi
 }
 
 build_projects()