Avoid Finder window flash during install

Signed-off-by: Dan Luhring <dan.luhring@anchore.com>

install.sh

@@ -243,7 +243,7 @@ unpack() {
 extract_from_dmg() {
   dmg_file=$1
   mount_point="/Volumes/tmp-dmg"
-  hdiutil attach -quiet -mountpoint "${mount_point}" "${dmg_file}"
+  hdiutil attach -quiet -nobrowse -mountpoint "${mount_point}" "${dmg_file}"
   cp -fR "${mount_point}/" ./
   hdiutil detach -quiet -force "${mount_point}"
 }