Rearrange build files to support USE_SOONG=true

Building with USE_SOONG=true will build with an Android.bp file if it is
present in the directory, otherwise an Android.mk file.  Only a few of
the bionic directories compile with soong, so include all of them from
the top level Android.mk file and remove the top level Android.bp file.
Individual subdirectories with Android.bp files will use soong with
USE_SOONG=true.

Change-Id: Idf8d7977ea4668fa646be25b543bf9d3773de615

Android.bp

@@ -1 +0,0 @@
-subdirs = ["*"]

Android.mk

@@ -16,4 +16,5 @@
 
 LOCAL_PATH := $(call my-dir)
 
-include $(call all-subdir-makefiles)
+include $(call all-makefiles-under,$(LOCAL_PATH)) \
+	$(call all-makefiles-under,$(LOCAL_PATH)/libc)

libc/Android.mk

@@ -1629,6 +1629,3 @@ LOCAL_SANITIZE := never
 LOCAL_NATIVE_COVERAGE := $(bionic_coverage)
 include $(BUILD_STATIC_LIBRARY)
 
-
-# ========================================================
-include $(call all-makefiles-under,$(LOCAL_PATH))