Let build.sh work when sha1sum also returns the filename

It seems this script was written for an sha1sum command that only
returns the sum, but my version also returns the filename. This should
now work for both.

Author: matthijskooijman

build.sh

@@ -7,7 +7,7 @@ docker rm webc || true
 if test -s /tmp/$desc.iso
 then
         dir=$(date --rfc-3339=date)/$desc
-        sha1=$(sha1sum /tmp/$desc.iso)
+        sha1=$(sha1sum /tmp/$desc.iso | cut -d' ' -f 1)
         mkdir -p $dir
         mv /tmp/$desc.iso $dir/$sha1.iso
         ln -sf $dir/$sha1.iso latest.iso