support/download: restore mandatory check of hashes

Now that custom external toolchains to be downloaded properly instruct
to not fail on a missing hash, restore the mandatory hash check for
everything else.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

support/download/check-hash

@@ -106,5 +106,5 @@ if [ ${nb_checks} -eq 0 ]; then
         ;;
     esac
     printf "ERROR: No hash found for %s\n" "${base}" >&2
-    exit 0
+    exit 3
 fi