Add module-target-built-files function

This is similar to module-built-files, except that it only returns
files built for the target, not the host.

Bug: 119423884
Test: Build with the no-vendor-variant VNDK change that uses this
      function.

Change-Id: I2a3d99003b05999eae01c0b90bb62b5263d65592
diff --git a/core/dpi_specific_apk.mk b/core/dpi_specific_apk.mk
index ad734b5..ad073c7 100644
--- a/core/dpi_specific_apk.mk
+++ b/core/dpi_specific_apk.mk
@@ -67,6 +67,7 @@
 ALL_MODULES += $(dpi_apk_name)
 ALL_MODULES.$(dpi_apk_name).CLASS := APPS
 ALL_MODULES.$(dpi_apk_name).BUILT := $(built_dpi_apk)
+ALL_MODULES.$(dpi_apk_name).TARGET_BUILT := $(built_dpi_apk)
 PACKAGES := $(PACKAGES) $(dpi_apk_name)
 PACKAGES.$(dpi_apk_name).PRIVATE_KEY := $(private_key)
 PACKAGES.$(dpi_apk_name).CERTIFICATE := $(certificate)