Disable -Wcast-calling-convention for vulkan

The following warning is triggered by the upcoming Clang update to
r271374:

frameworks/native/vulkan/libvulkan/stubhal.cpp:114:12: error: cast
between incompatible calling conventions 'cdecl' and 'aapcs-vfp'; calls
through thispointer may abort at runtime
[-Werror,-Wcast-calling-convention]
    return reinterpret_cast<PFN_vkVoidFunction>(NoOp);

Change-Id: I8de75fd6a3b579a91598aebbdd23bf74b57c3593
(cherry picked from commit b4c0eb1d203f88f0ef9ef9c360c03bcbb3e90efc)
diff --git a/vulkan/libvulkan/Android.mk b/vulkan/libvulkan/Android.mk
index d2e28ff..4d2cffc 100644
--- a/vulkan/libvulkan/Android.mk
+++ b/vulkan/libvulkan/Android.mk
@@ -25,7 +25,9 @@
 	-Weverything -Werror \
 	-Wno-padded \
 	-Wno-switch-enum \
-	-Wno-undef
+	-Wno-undef \
+	-Wno-cast-calling-convention
+
 #LOCAL_CFLAGS += -DLOG_NDEBUG=0
 LOCAL_CPPFLAGS := -std=c++14 \
 	-Wno-c99-extensions \