Overwrite android-info instead of appending to it

if someone changes board-info.txt, then it should be copied out to
 out/target/product/<device>/android-info.txt, instead of appending.
diff --git a/target/board/Android.mk b/target/board/Android.mk
index 7137082..ac8cb44 100644
--- a/target/board/Android.mk
+++ b/target/board/Android.mk
@@ -46,7 +46,7 @@
 $(INSTALLED_ANDROID_INFO_TXT_TARGET): $(board_info_txt)
 	$(call pretty,"Generated: ($@)")
 ifdef board_info_txt
-	$(hide) cat $< >> $@
+	$(hide) cat $< > $@
 else
 	$(hide) echo "board=$(TARGET_BOOTLOADER_BOARD_NAME)" > $@
 endif