Add libunwind_llvm.

Change-Id: I072637cc6f06f19e4d08e66242f5d9daeec6a1fd

default.xml

@@ -205,6 +205,7 @@
   <project path="external/libselinux" name="platform/external/libselinux" groups="pdk" />
   <project path="external/libssh2" name="platform/external/libssh2" groups="pdk-cw-fs" />
   <project path="external/libunwind" name="platform/external/libunwind" groups="pdk" />
+  <project path="external/libunwind_llvm" name="platform/external/libunwind_llvm" />
   <project path="external/libusb" name="platform/external/libusb" groups="pdk-cw-fs" />
   <project path="external/libusb-compat" name="platform/external/libusb-compat" groups="pdk-cw-fs" />
   <project path="external/libutf" name="platform/external/libutf" groups="pdk-cw-fs" />