setup: add option to install.sh to skip resizing

Use "... | bash -s norootshrink" to skip shrinking the root partition,
for the case where an external drive will be used for subsequent setup.

setup/generic/install.sh

@@ -58,7 +58,7 @@ lastpart=$(sfdisk -q -l "$rootdev" | tail +2 | sort -n -k 2 | tail -1 | awk '{pr
 # TODO: provide a way to skip this, to support having boot+root on
 # eMMC or sd card, and storage elsewhere
 unpart=$(sfdisk -F "$rootdev" | grep -o '[0-9]* bytes' | head -1 | awk '{print $1}')
-if [ "$unpart" -lt  $(( (1<<30) * 32)) ]
+if [ "${1:-}" != "norootshrink" ] && [ "$unpart" -lt  $(( (1<<30) * 32)) ]
 then
   # This script will only shrink the root partition, and if there's another
   # partition following the root partition, we won't be able to grow the
@@ -98,9 +98,6 @@ then
 		EOF
     chmod a+x /etc/rc.local
 
-    # The user should have configured networking manually, so disable wifi setup
-    touch /teslausb/WIFI_ENABLED
-
     if [ ! -e "/boot/initrd.img-$(uname -r)" ]
     then
       # This device did not boot using an initramfs. If we're running
@@ -165,6 +162,9 @@ then
   done
 fi
 
+# The user should have configured networking manually, so disable wifi setup
+touch /teslausb/WIFI_ENABLED
+
 # Copy our rc.local from github, which will allow setup to
 # continue using the regular "one step setup" process used
 # for setting up a Raspberry Pi with the prebuilt image