Update rules for libpixelfinger_twrp

Change-Id: I40131f330e902afab033e810761bf98c07bbd03d
diff --git a/libpixelflinger/Android.mk b/libpixelflinger/Android.mk
index 693a612..99f026c 100644
--- a/libpixelflinger/Android.mk
+++ b/libpixelflinger/Android.mk
@@ -15,13 +15,17 @@
 
 PIXELFLINGER_SRC_FILES += \
     codeflinger/CodeCache.cpp \
-    codeflinger/tinyutils/SharedBuffer.cpp \
-    codeflinger/tinyutils/VectorImpl.cpp \
     format.cpp \
     clear.cpp \
     raster.cpp \
     buffer.cpp
 
+ifneq ($(wildcard system/core/libpixelflinger/codeflinger/tinyutils/VectorImpl.cpp),)
+    PIXELFLINGER_SRC_FILES += \
+        codeflinger/tinyutils/SharedBuffer.cpp \
+        codeflinger/tinyutils/VectorImpl.cpp
+endif
+
 ifneq ($(TW_HAVE_X86_ACCELERATED_PIXELFLINGER),true)
 PIXELFLINGER_SRC_FILES += \
 	codeflinger/ARMAssemblerInterface.cpp \