explicitly detach loop device on umount

I see cases where a stale loop device stays around and fills up my
partition as image file is still in use and does not get unlinked.

Explicitly detach loop device on umount to fix that.

Signed-off-by: Christian Hesse <mail@eworm.de>

archiso/mkarchiso

@@ -59,7 +59,7 @@ _mount_airootfs() {
 
 _umount_airootfs() {
     _msg_info "Unmounting '${work_dir}/mnt/airootfs'"
-    umount "${work_dir}/mnt/airootfs"
+    umount -d "${work_dir}/mnt/airootfs"
     _msg_info "Done!"
     rmdir "${work_dir}/mnt/airootfs"
     trap - EXIT HUP INT TERM

configs/releng/build.sh

@@ -190,7 +190,7 @@ make_efiboot() {
     cp ${work_dir}/iso/EFI/shellx64_v2.efi ${work_dir}/efiboot/EFI/
     cp ${work_dir}/iso/EFI/shellx64_v1.efi ${work_dir}/efiboot/EFI/
 
-    umount ${work_dir}/efiboot
+    umount -d ${work_dir}/efiboot
 }
 
 # Build airootfs filesystem image