Building qemu fails on Solaris 11.4
Description of problem:
Building qemu-system-hppa on Solaris 11.4 (details above) fails because in qga/commands-posix.c

(1) Solaris does not have net/ethernet.h
```
 #if defined(__NetBSD__) || defined(__OpenBSD__)
 #include <net/if_arp.h>
 #include <netinet/if_ether.h>
 #else
 #include <net/ethernet.h>
 #endif
```
Solaris *does* have net/if_arp.h and netinet/if_ether.h

(2) Solaris does not define ETHER_ADDR_LEN, instead it defines ETHERADDRL
Steps to reproduce:
1. '../configure' '--disable-docs' '--disable-rdma' '--target-list=hppa-softmmu'
2. gmake
Additional information: