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

Change-Id: I3c75d093bb48a9d10952d587c3e48bbcc227f139
diff --git a/target/board/generic/BoardConfig.mk b/target/board/generic/BoardConfig.mk
index 2b72d01..9e52d25 100644
--- a/target/board/generic/BoardConfig.mk
+++ b/target/board/generic/BoardConfig.mk
@@ -9,3 +9,6 @@
 TARGET_CPU_ABI := armeabi
 HAVE_HTC_AUDIO_DRIVER := true
 BOARD_USES_GENERIC_AUDIO := true
+
+# no hardware camera
+USE_CAMERA_STUB := true