mkarchiso: unset TMPDIR to work around FS#70580

Alternative to 3d6651ab which caused issues.

Fixes https://bugs.archlinux.org/task/70580 .

archiso/mkarchiso

@@ -329,10 +329,11 @@ _make_packages() {
         export ARCHISO_GNUPG_FD
     fi
 
+    # Unset TMPDIR to work around https://bugs.archlinux.org/task/70580
     if [[ "${quiet}" = "y" ]]; then
-        pacstrap -C "${work_dir}/${buildmode}.pacman.conf" -c -G -M -- "${pacstrap_dir}" "${buildmode_pkg_list[@]}" &> /dev/null
+        env -u TMPDIR pacstrap -C "${work_dir}/${buildmode}.pacman.conf" -c -G -M -- "${pacstrap_dir}" "${buildmode_pkg_list[@]}" &> /dev/null
     else
-        pacstrap -C "${work_dir}/${buildmode}.pacman.conf" -c -G -M -- "${pacstrap_dir}" "${buildmode_pkg_list[@]}"
+        env -u TMPDIR pacstrap -C "${work_dir}/${buildmode}.pacman.conf" -c -G -M -- "${pacstrap_dir}" "${buildmode_pkg_list[@]}"
     fi
 
     if [[ -n "${gpg_key}" ]]; then
@@ -374,7 +375,8 @@ _make_customize_airootfs() {
         _msg_info "Running customize_airootfs.sh in '${pacstrap_dir}' chroot..."
         _msg_warning "customize_airootfs.sh is deprecated! Support for it will be removed in a future archiso version."
         chmod -f -- +x "${pacstrap_dir}/root/customize_airootfs.sh"
-        eval -- arch-chroot "${pacstrap_dir}" "/root/customize_airootfs.sh"
+        # Unset TMPDIR to work around https://bugs.archlinux.org/task/70580
+        eval -- env -u TMPDIR arch-chroot "${pacstrap_dir}" "/root/customize_airootfs.sh"
         rm -- "${pacstrap_dir}/root/customize_airootfs.sh"
         _msg_info "Done! customize_airootfs.sh run successfully."
     fi