Add platform/external/piex

Change-Id: I20a2d009e89b1d9df101af0a445fdf635fc758dc

default.xml

@@ -254,6 +254,7 @@
   <project path="external/parameter-framework" name="platform/external/parameter-framework" groups="pdk-fs" />
   <project path="external/pcre" name="platform/external/pcre" groups="pdk" />
   <project path="external/pdfium" name="platform/external/pdfium" groups="pdk" />
+  <project path="external/piex" name="platform/external/piex" />
   <project path="external/ppp" name="platform/external/ppp" groups="pdk-cw-fs,pdk-fs" />
   <project path="external/proguard" name="platform/external/proguard" groups="pdk" />
   <project path="external/protobuf" name="platform/external/protobuf" groups="pdk" />