[Openais] [PATCH] build: silence automake portability warnings

[Jim Meyering]

Without this patch, running automake provokes this:

  exec/Makefile.am:66: SHARED_LIBS:%.so.$(SONAME: non-POSIX variable name
  exec/Makefile.am:67: SHARED_LIBS:%.so.$(SONAME: non-POSIX variable name
  exec/Makefile.am:77: `%'-style pattern rules are a GNU make extension
  exec/Makefile.am:97: `%'-style pattern rules are a GNU make extension
  lcr/Makefile.am:53: `%'-style pattern rules are a GNU make extension
  lcr/Makefile.am:56: `%'-style pattern rules are a GNU make extension
  lib/Makefile.am:78: `%'-style pattern rules are a GNU make extension
  lib/Makefile.am:101: `%'-style pattern rules are a GNU make extension
  man/Makefile.am:104: `%'-style pattern rules are a GNU make extension
  pkgconfig/Makefile.am:42: `%'-style pattern rules are a GNU make extension
  pkgconfig/Makefile.am:53: `%'-style pattern rules are a GNU make extension
  services/Makefile.am:53: `%'-style pattern rules are a GNU make extension
  services/Makefile.am:56: `%'-style pattern rules are a GNU make extension
  services/Makefile.am:59: `%'-style pattern rules are a GNU make extension
  services/Makefile.am:62: `%'-style pattern rules are a GNU make extension
  services/Makefile.am:66: `%'-style pattern rules are a GNU make extension

With the patch, automake is silent.