Fix jenkins release build script

Properly build the source package.

hudson_build_release.sh

@@ -3,6 +3,8 @@
 cd simgear
 cmake -DCMAKE_INSTALL_PREFIX:PATH=$WORKSPACE/dist
 
+# first make source package (clean directory), finally compile
+make package_source
 make
 
 if [ $? -ne '0' ]; then
@@ -11,12 +13,14 @@ if [ $? -ne '0' ]; then
 fi
 
 make install
-make dist
 
 echo "Starting on FlightGear"
 
 cd ../flightgear
 cmake -DCMAKE_INSTALL_PREFIX:PATH=$WORKSPACE/dist
+
+# first source package (clean directory), finally compile
+make package_source
 make
 
 if [ $? -ne '0' ]; then
@@ -25,4 +29,4 @@ if [ $? -ne '0' ]; then
 fi
 
 make install
-make dist
+