lib: retry git fetch a few times (take 2)

Wrap the failure in a if statement. Otherwise it will fail the first
time because the script runs under -e

lib/build.sh

@@ -26,9 +26,12 @@ if ! [[ "$ref" =~ ^refs/ ]] ; then
     ref=refs/heads/$ref
 fi
 for retry in 1 2 3 ; do
-    timeout 15m git fetch --update-head-ok origin +$ref:$ref && break
+    if timeout 15m git fetch --update-head-ok origin +$ref:$ref ; then
+	break
+    else
 	echo "Retry git fetch in 60 seconds"
 	sleep 60
+    fi
 done
 git fetch --update-head-ok origin +$ref:$ref
 git switch --force-create $v $ref