Introduce TARGET_BUILD_PDK for selecting build tweaks for the PDK

BUILD_PDK and some of the other infrastructure will go away once
we're done with the new new PDK work, but for now don't disturb
that stuff.

Change-Id: Ia39bf759ec03f203858ddcc4880af72bd132cb5a
diff --git a/core/Makefile b/core/Makefile
index 173932c..e005485 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -631,7 +631,7 @@
 # Recovery image
 
 # If neither TARGET_NO_KERNEL nor TARGET_NO_RECOVERY are true
-ifeq (,$(filter true, $(TARGET_NO_KERNEL) $(TARGET_NO_RECOVERY) $(BUILD_TINY_ANDROID) $(BUILD_PDK)))
+ifeq (,$(filter true, $(TARGET_NO_KERNEL) $(TARGET_NO_RECOVERY) $(BUILD_TINY_ANDROID) $(TARGET_BUILD_PDK)))
 
 INSTALLED_RECOVERYIMAGE_TARGET := $(PRODUCT_OUT)/recovery.img
 
diff --git a/core/main.mk b/core/main.mk
index ab9d52d..a038d5d 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -218,7 +218,8 @@
 endif
 ifneq ($(PDK_BUILD_TYPE),)
   $(info PDK build type $(PDK_BUILD_TYPE))
-  BUILD_PDK:= true
+  BUILD_PDK:=true
+  TARGET_BUILD_PDK:=true
   include pdk/build/pdk.mk
   # force droid target
   MAKECMDGOALS:= $(subst $(PDK_BUILD_TYPE),droid,$(MAKECMDGOALS))
@@ -729,7 +730,7 @@
 ifeq ($(BUILD_TINY_ANDROID), true)
 INSTALLED_RECOVERYIMAGE_TARGET :=
 endif
-ifneq ($(BUILD_PDK),)
+ifneq ($(TARGET_BUILD_PDK),)
 INSTALLED_RECOVERYIMAGE_TARGET :=
 endif
 
diff --git a/core/tasks/apicheck.mk b/core/tasks/apicheck.mk
index b3d800b..8d9928e 100644
--- a/core/tasks/apicheck.mk
+++ b/core/tasks/apicheck.mk
@@ -18,7 +18,7 @@
 #
 
 # skip api check for TINY_ANDROID and PDK buid
-ifeq (,$(filter true, $(BUILD_TINY_ANDROID) $(BUILD_PDK)))
+ifeq (,$(filter true, $(BUILD_TINY_ANDROID) $(TARGET_BUILD_PDK)))
 
 .PHONY: checkapi