Remove obsolete PDK build functionality

This hasn't worked for a couple years, and continues to bitrot. Just
remove it.

Test: treehugger
Change-Id: Iea6caf3c08252a560155e095135c5ddaad712991
Merged-In: Iea6caf3c08252a560155e095135c5ddaad712991
diff --git a/core/distdir.mk b/core/distdir.mk
index 5f40407..aad8ff3 100644
--- a/core/distdir.mk
+++ b/core/distdir.mk
@@ -28,7 +28,7 @@
 # certain files with certain goals.  When those goals are built
 # and "dist" is specified, the marked files will be copied to DIST_DIR.
 #
-# $(1): a list of goals  (e.g. droid, sdk, pdk, ndk). These must be PHONY
+# $(1): a list of goals  (e.g. droid, sdk, ndk). These must be PHONY
 # $(2): the dist files to add to those goals.  If the file contains ':',
 #       the text following the colon is the name that the file is copied
 #       to under the dist directory.  Subdirs are ok, and will be created