update_submodules: Use relative paths to submodules

There doesn't seem to be much reason to use absolute paths to the
submodules, other than that it's not needed to change to the original
directory.

In preparation for CB:87824, make use of relative paths and change to
the original directory at the start of each iteration.

Change-Id: Ic74b589d933e6acd882fb9a09461bf7c01952a6f
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/87823
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>

util/scripts/update_submodules

@@ -65,7 +65,7 @@ get_args() {
 			exit 0
 			;;
 		-R | --repo)
-			submodule_dirs=("$(readlink -f "${1}")")
+			submodule_dirs="${1}"
 			shift
 			if [[ ! -d "${submodule_dirs[0]}" ]]; then
 				echo "Error: ${submodule_dirs[0]} is not valid."
@@ -92,12 +92,15 @@ main() {
 	get_args "$@"
 
 	if (( ${#submodule_dirs[@]} == 0 )); then
-		readarray -t submodule_dirs < <(git submodule foreach pwd | grep -v "Entering")
+		readarray -t submodule_dirs < <(git submodule status | cut -d ' ' -f 3)
 	fi
 
 	for submodule in "${submodule_dirs[@]}"; do
+		cd "${TOP}"
+
 		echo ""
 		echo "Checking submodule ${submodule}"
+
 		if ! cd "$submodule"; then
  			echo "Error: could not cd to $submodule"
 			exit 1