ci(coverity): don't sanitise job count

For whatever reason, `clean_build` parameters are not correctly expanded
by the shell. As a temporary work-around, don't escape the job count.

Change-Id: Ie84b86b248bd1be49b708e4e19780c4f3d175907
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/script/tf-coverity/common-def.sh b/script/tf-coverity/common-def.sh
index 2b46130..5ef6609 100644
--- a/script/tf-coverity/common-def.sh
+++ b/script/tf-coverity/common-def.sh
@@ -44,7 +44,7 @@
     debug="DEBUG=1"
     [ -n "$release" ] && debug=""
 
-    echo " -j ${jobs@Q} $debug -s "
+    echo " --jobs=${jobs} $debug -s "
 }
 
 # Check if execution environment is ARM's jenkins (Jenkins running under ARM