image_to_vm.sh: delete unused build_common.sh

None of the funcs in here are used anymore, so stop loading it.

BUG=chromium:1145812
TEST=CQ passes

Change-Id: I1040106d52f1d161fafb1b814882a2e0649d37e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/2648862
Tested-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Shao-Chuan Lee <shaochuan@chromium.org>
Reviewed-by: Shao-Chuan Lee <shaochuan@chromium.org>
diff --git a/image_to_vm.sh b/image_to_vm.sh
index 4d5a0e7..ce66b94 100755
--- a/image_to_vm.sh
+++ b/image_to_vm.sh
@@ -9,7 +9,6 @@
 # Helper scripts should be run from the same location as this script.
 SCRIPT_ROOT=$(dirname "$(readlink -f "$0")")
 . "${SCRIPT_ROOT}/common.sh" || exit 1
-. "${SCRIPT_ROOT}/build_library/build_common.sh" || exit 1
 . "${SCRIPT_ROOT}/build_library/ext2_sb_util.sh" || exit 1
 
 # Need to be inside the chroot to load chromeos-common.sh