Added support for building libetpan locally.

Normally the build-dep.sh script downloads libetpan (and other dependancies) during a mail core build. Since we have a patched libetpan library we need to use a locally built version. This patch modifies the build-dep script to check the built products directory for a .a file that matches the dependancy, and if it is there doesn't perform a version check and doesn't download a new version. There are a few problems with this approach:

1, libetpan must be built by the umbrella build before mailcore2 targets are built, otherwise a new version will still be downloaded.
2. The dependancy detection only works for .a targets, where build-dep.sh can support other target types.
3. If libetpan is built locally its version is not checked, so the version in the umbrella build must be compatible.

Author: MythicLionMan

scripts/include.sh/build-dep.sh

@@ -330,7 +330,20 @@ get_prebuilt_dep()
 
   installed_version="`defaults read "$installed_versions_path" "$name" 2>/dev/null`"
   if test ! -d "$scriptpath/../Externals/$name" ; then
-    installed_version=
+    echo "$name is not in Externals. Checking built products dir"
+
+    if test -f "${BUILT_PRODUCTS_DIR}/${name}.a" ; then
+      echo "Found product in built products dir, using that version. The version number of that"
+      echo "version is unknown, it is your responsability to ensure that it is up to date and is"
+      echo "configured properly with any required headers copied to $BUILT_PRODUCTS_DIR"
+
+      # Mark the version as up to date, even though the true version number is not known
+      installed_version="`defaults read "$versions_path" "$name" 2>/dev/null`"
+    else
+      # There is no version in BUILT_PRODUCTS_DIR so clear installed_version in order to 
+      # download a new copy
+      installed_version=
+    fi
   fi
   if test "x$installed_version" = x ; then
     installed_version="none"