fd-send-recv.1.0.0: Make invocation of `make` portable
mirage-net-direct.0.9.1: Make invocation of `make` portable
mirage-net-direct.0.9.2: Make invocation of `make` portable
mirage-net-socket.0.9.1: Make invocation of `make` portable
mirage-net-socket.0.9.2: Make invocation of `make` portable
Merge pull request #889 from pgj/master

Further make(1) portability fixes