Set no camera default for emulator/generic/sim builds.

Change-Id: I3c75d093bb48a9d10952d587c3e48bbcc227f139
diff --git a/target/board/sim/BoardConfig.mk b/target/board/sim/BoardConfig.mk
index 491b30f..3d83e7b 100644
--- a/target/board/sim/BoardConfig.mk
+++ b/target/board/sim/BoardConfig.mk
@@ -23,3 +23,6 @@
 #the simulator partially emulates the original HTC /dev/eac audio interface
 HAVE_HTC_AUDIO_DRIVER := true
 BOARD_USES_GENERIC_AUDIO := true
+
+# no hardware camera
+USE_CAMERA_STUB := true