Add -Wno-unused-parameter to suppress the warning.

For example in system/core/libcorkscrew/arch-arm/backtrace-arm.c:

system/core/libcorkscrew/arch-arm/backtrace-arm.c:555:49: error: unused
parameter 'siginfo' [-Werror=unused-parameter]

Change-Id: Ibe13e8761a2f57324c0f0d87d9add549a20aa37a
diff --git a/libcorkscrew/Android.mk b/libcorkscrew/Android.mk
index d62c2d5..e275317 100644
--- a/libcorkscrew/Android.mk
+++ b/libcorkscrew/Android.mk
@@ -51,7 +51,7 @@
 
 LOCAL_SHARED_LIBRARIES += libdl libcutils liblog libgccdemangle
 
-LOCAL_CFLAGS += -std=gnu99 -Werror
+LOCAL_CFLAGS += -std=gnu99 -Werror -Wno-unused-parameter
 LOCAL_MODULE := libcorkscrew
 LOCAL_MODULE_TAGS := optional
 
@@ -81,7 +81,7 @@
   LOCAL_SHARED_LIBRARIES += libgccdemangle # TODO: is this even needed on Linux?
   LOCAL_LDLIBS += -lrt
 endif
-LOCAL_CFLAGS += -std=gnu99 -Werror
+LOCAL_CFLAGS += -std=gnu99 -Werror -Wno-unused-parameter
 LOCAL_MODULE := libcorkscrew
 LOCAL_MODULE_TAGS := optional
 include $(BUILD_HOST_SHARED_LIBRARY)