Fixed offset of partition on iso

Split from commit 00dda7d4 from Svenstaro repo: changed -offset for mkarchiso
from default 0 to 1 so that the other partition on the usb device can
still be edited after dd'ing to it

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

archiso/mkarchiso

@@ -247,7 +247,7 @@ command_iso () {
         -A "${APPLICATION}" \
         -V "${LABEL}" \
         -o "${imgname}" "${work_dir}/iso/"
-    isohybrid "${imgname}"
+    isohybrid -offset 1 "${imgname}"
 }
 
 # Go through the main commands in order. If 'all' was specified, then we want