Proper argument escaping for special characters.

Fixes side note of QubesOS/qubes-issues#5562

(cherry picked from commit c600b1b39c)

dom0-updates/qubes-dom0-update

@@ -1,13 +1,13 @@
 #!/bin/bash
 
-quote_args() {
-    local quoted_args=""
+escape_args() {
+    local eargs=""
 
-    for arg in "${@}"; do
-        quoted_args="${quoted_args} \"${arg}\""
+    for arg in "$@"; do
+	printf -v eargs '%s%q ' "$eargs" "$arg"
     done
 
-    echo "${quoted_args}"
+    echo "${eargs%?}"
 }
 
 find_regex_in_args() {
@@ -201,7 +201,7 @@ qvm-run --nogui -q $UPDATEVM 'rm -rf /var/lib/qubes/dom0-updates/etc' || exit 1
 tar c /var/lib/rpm /etc/yum.repos.d /etc/yum.conf 2>/dev/null | \
    qvm-run --nogui -q --pass-io "$UPDATEVM" 'LC_MESSAGES=C tar x -C /var/lib/qubes/dom0-updates 2>&1 | grep -v -E "s in the future"'
 
-qvm-run $QVMRUN_OPTS --pass-io $UPDATEVM "script --quiet --return --command '/usr/lib/qubes/qubes-download-dom0-updates.sh --doit --nogui $(quote_args "${ALL_OPTS[@]}")' /dev/null" < /dev/null
+qvm-run $QVMRUN_OPTS --pass-io $UPDATEVM "script --quiet --return --command '/usr/lib/qubes/qubes-download-dom0-updates.sh --doit --nogui $(escape_args "${ALL_OPTS[@]}")' /dev/null" < /dev/null
 RETCODE=$?
 if [ "$CHECK_ONLY" == "1" ]; then
     exit $RETCODE