Silence uninteresting warnings.

Upstream doesn't seem to care about signed/unsigned or pointer arithmetic
warnings, so there's little point us looking at them.

The remaining one is weird though --- given that this is an inline function
in os/os-linux.h, how does this link?

  external/fio/idletime.c: In function 'idle_prof_thread_fn':
  external/fio/idletime.c:92:2: warning: implicit declaration of function 'fio_set_sched_idle' [-Wimplicit-function-declaration]
    if ((retval = fio_set_sched_idle()))
    ^

Change-Id: I27efbe3b18a46a5253c2edd464b655d995c82024
diff --git a/Android.mk b/Android.mk
index b05c494..6dd3e35 100644
--- a/Android.mk
+++ b/Android.mk
@@ -98,8 +98,12 @@
                 -g \
                 -rdynamic \
                 -std=gnu99 \
+                -Wno-pointer-arith \
+                -Wno-sign-compare \
 
 LOCAL_CFLAGSS_64 += \
                 -DCONFIG_LINUX_SPLICE \
 
+LOCAL_ADDITIONAL_DEPENDENCIES += $(LOCAL_PATH)/Android.mk
+
 include $(BUILD_EXECUTABLE)