fix --rbdir is ignored in configure

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28629 a1c6a512-1295-4272-9138-f99709370657

tools/configure

@@ -102,7 +102,7 @@ app_get_platform() {
                 bindir="$ARG_PREFIX/bin"
                 libdir="$ARG_PREFIX/lib"
             else
-                echo "ERROR: PREFIX does not does not exist"
+                echo "ERROR: PREFIX does not exist"
                 exit
             fi
         fi
@@ -3120,6 +3120,13 @@ else
 fi
 
 if [ "$ARG_RBDIR" ]; then
+  if [ "$need_full_path" != "yes" ]; then
+    if [ -z `echo $ARG_RBDIR | grep '^/'` ]; then
+        rbdir="/"$ARG_RBDIR
+    else
+        rbdir=$ARG_RBDIR
+    fi
+  fi
   echo "Using alternate rockbox dir: ${rbdir}"
 fi