MIPS generic target support

Change-Id: I76506eba9d11867e53069c97038996bddd7dd5a2
Signed-off-by: Chris Dearman <chris@mips.com>
Signed-off-by: Raghu Gandham <raghu@mips.com>
Signed-off-by: Duane Sand <duanes@mips.com>
Signed-off-by: Bhanu Chetlapalli <bhanu@mips.com>
diff --git a/target/board/generic/BoardConfig.mk b/target/board/generic/BoardConfig.mk
index 57e60d3..b25abb0 100644
--- a/target/board/generic/BoardConfig.mk
+++ b/target/board/generic/BoardConfig.mk
@@ -34,7 +34,9 @@
 # Enable dex-preoptimization to speed up the first boot sequence
 # of an SDK AVD. Note that this operation only works on Linux for now
 ifeq ($(HOST_OS),linux)
-WITH_DEXPREOPT := true
+  ifeq ($(WITH_DEXPREOPT),)
+    WITH_DEXPREOPT := true
+  endif
 endif
 
 # Build OpenGLES emulation guest and host libraries