[build] Fix strict prototype warning with latest Clang.

https://reviews.llvm.org/D122895 changed the semantics of Clang's
-Wstrict-prototypes, which causes the following warning to be emitted:

  android-emu/android/base/ring_buffer.c:45:37: warning: a function
    declaration without a prototype is deprecated in all versions of C"

This change fixes the warning to allow building with the latest Clang at
-Werror.

Change-Id: I3fd3caad2cdeddc74390f500e620c52948decc07
1 file changed