buildscript: do not overwrite build directory on prepare

So far, we remove the old and copy a fresh new OpenWrt directory
into the build directory on prepare. There is no need to do this,
as OpenWrt/Make is capable of detecting changes and we do properly
update the feeds and patches already.

So, just clone the OpenWrt main repo into builddir directly, and
just checkout/apply patches during prepare.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

buildscript

@@ -62,6 +62,11 @@ checkout_git(){
     if [ -d "$DIRECTORY" ]; then
         if $MYGIT remote -v | grep -q "$REPO_URL" ; then
             echo "Right remote detected"
+            # Reset tracked files
+            $MYGIT reset --hard HEAD
+            # Remove untracked files
+            $MYGIT clean -f -d
+            # Select desired commit
             if ! $MYGIT checkout "$COMMITID" ; then
                 echo "commitid not found trying to fetch new commits"
                 $MYGIT pull && $MYGIT checkout "$COMMITID"
@@ -82,14 +87,11 @@ checkout_git(){
 }
 
 get_source() {
-    test -d src || mkdir src
-    cd src
+    #Get the OpenWrt main repo
+    checkout_git $builddir $OPENWRTURL $OPENWRTREV
 
-    #Get the OpenWrt Core Source for Firmware
-    checkout_git openwrt $OPENWRTURL $OPENWRTREV
-
-    test -d packages || mkdir packages
-    cd packages
+    test -d src/packages || mkdir -p src/packages
+    cd src/packages
 
     #checkout needed package feeds
     for FEEDVAR in "${FEEDS[@]}" ; do
@@ -129,11 +131,6 @@ patch_target() {
 prepare() {
     get_source
 
-    test -d $builddir || mkdir $builddir
-
-    /bin/rm -rf "$builddir"
-    cp -a src/openwrt "$builddir"
-
     patch_target
 
     # apply variant to ensure the included file "variant.mk"
@@ -342,7 +339,7 @@ buildrelease() {
 }
 
 clean() {
-    /bin/rm -rf bin $builddir src/openwrt
+    /bin/rm -rf bin $builddir
 
     # remove downloaded package feeds
     for FEEDVAR in "${FEEDS[@]}" ; do