allow installation in qemu

Currently, installation is only supported on real hardware, but not
running in QEMU. Change the check to make sure the necessary
directories and programs are available instead of bailing out
on non-Raspberry archs.

install.sh

@@ -5,9 +5,26 @@ if [[ $EUID -ne 0 ]]; then
    exit 1
 fi
 
-is_Raspberry=$(cat /proc/device-tree/model | awk  '{print $1}')
-if [ "x${is_Raspberry}" != "xRaspberry" ] ; then
-  echo "Sorry, this drivers only works on raspberry pi"
+#
+# make sure that we are on something ARM/Raspberry related
+# either a bare metal Raspberry or a qemu session with 
+# Raspberry stuff available
+# - check for /boot/overlays
+# - dtparam and dtoverlay is available
+errorFound=0
+if [ ! -d /boot/overlays ] ; then
+  echo "/boot/overlays not found or not a directory" 1>&2
+  errorFound=1
+fi
+# should we also check for alsactl and amixer used in seeed-voicecard?
+for cmd in dtparam dtoverlay ; do
+  if ! which $cmd &>/dev/null ; then
+    echo "$cmd not found" 1>&2
+    errorFound=1
+  fi
+done
+if [ $errorFound = 1 ] ; then
+  echo "Errors found, exiting." 1>&2
   exit 1
 fi