Use new -ninja flag to aidl-cpp

This make aidl-cpp write out a dep file that ninja parses correctly.

Test: Manually inspect ninja depfile
Change-Id: I4890a91eb29a6388e17b1ffac23a3dc0ffe6c212
diff --git a/core/binary.mk b/core/binary.mk
index be1432e..c11ed32f 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -953,7 +953,7 @@
 $(foreach s,$(aidl_src),\
     $(eval $(call define-aidl-cpp-rule,$(s),$(aidl_gen_cpp_root),aidl_gen_cpp)))
 $(foreach cpp,$(aidl_gen_cpp), \
-    $(call include-depfile,$(addsuffix .aidl.P,$(basename $(cpp))),$(cpp)))
+    $(call include-depfile,$(addsuffix .aidl.d,$(basename $(cpp))),$(cpp)))
 $(call track-src-file-gen,$(aidl_src),$(aidl_gen_cpp))
 
 $(aidl_gen_cpp) : PRIVATE_MODULE := $(LOCAL_MODULE)
diff --git a/core/definitions.mk b/core/definitions.mk
index 2e7c9b3..7a42ad8 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -1063,7 +1063,7 @@
 @mkdir -p $(dir $@)
 @mkdir -p $(PRIVATE_HEADER_OUTPUT_DIR)
 @echo "Generating C++ from AIDL: $(PRIVATE_MODULE) <= $<"
-$(hide) $(AIDL_CPP) -d$(basename $@).aidl.P $(PRIVATE_AIDL_FLAGS) \
+$(hide) $(AIDL_CPP) -d$(basename $@).aidl.d -ninja $(PRIVATE_AIDL_FLAGS) \
     $< $(PRIVATE_HEADER_OUTPUT_DIR) $@
 endef