Add external/xz-embedded to the manifest.

Bug: http://b/32846435
Test: repo sync external/xz-embedded
Change-Id: I4f2c7dd8338f80827b0732f645b6b0dce05a2b92

default.xml

@@ -330,6 +330,7 @@
   <project path="external/xmlrpcpp" name="platform/external/xmlrpcpp" groups="pdk" />
   <project path="external/xmlwriter" name="platform/external/xmlwriter" groups="pdk" />
   <project path="external/xmp_toolkit" name="platform/external/xmp_toolkit" groups="pdk" />
+  <project path="external/xz-embedded" name="platform/external/xz-embedded" groups="pdk" />
   <project path="external/zlib" name="platform/external/zlib" groups="pdk" />
   <project path="external/zopfli" name="platform/external/zopfli" groups="pdk" />
   <project path="external/zxing" name="platform/external/zxing" groups="pdk" />