Remove import_includes/export_includes

Now that ONE_SHOT_MAKEFILE no longer exists, we don't have to rely on
the filesystem to store this informtion.

This removes ~16.7k files from our build graph
(aosp-master/aosp_arm64-eng), though only about 600 of them were being
used in a normal build.

Test: treehugger
Change-Id: I3ac12f5ea7f11d25064109a0599bc5be1976fba5
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 426e25d..032f6e5 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -646,6 +646,9 @@
 # link_type and jni_link_type files are no longer needed
 $(call add-clean-step, find $(OUT_DIR) -type f -name "*link_type" -print0 | xargs -0 rm -f)
 
+# import_includes and export_includes files are no longer needed
+$(call add-clean-step, find $(OUT_DIR) -type f -name "import_includes" -o -name "export_includes" -print0 | xargs -0 rm -f)
+
 # ************************************************
 # NEWER CLEAN STEPS MUST BE AT THE END OF THE LIST
 # ************************************************