Fix vpx_rtcd.h dependency in Android.mk

Failed to build on Linux (as described in Android.mk) with NDK r7b.
Set vpx_rtcd.h dependency after libvpx sources are added to
LOCAL_SRC_FILES so that vpx_rtcd.h is generated before any libvpx file
is touched.

Change-Id: Ibe19d485ca9f679dc084044df0e3fb14587c4d3e

build/make/Android.mk

@@ -121,7 +121,6 @@ $(ASM_CNV_PATH)/libvpx/%.asm.s: $(LIBVPX_PATH)/%.asm $(ASM_CNV_OFFSETS_DEPEND)
 # For building vpx_rtcd.h, which has a rule in libs.mk
 TGT_ISA:=$(word 1, $(subst -, ,$(TOOLCHAIN)))
 target := libs
-$(foreach file, $(LOCAL_SRC_FILES), $(LOCAL_PATH)/$(file)): vpx_rtcd.h
 
 LOCAL_SRC_FILES += vpx_config.c
 
@@ -169,6 +168,8 @@ LOCAL_LDLIBS := -llog
 
 LOCAL_STATIC_LIBRARIES := cpufeatures
 
+$(foreach file, $(LOCAL_SRC_FILES), $(LOCAL_PATH)/$(file)): vpx_rtcd.h
+
 .PHONY: clean
 clean:
 	@echo "Clean: ads2gas files [$(TARGET_ARCH_ABI)]"