message: Add FreeBSD support
  Treat FreeBSD like macOS (which is accurate in terms of development!)
  in the code to determine the MAC address of a network interface.
  With this change, vcpkg-tool compiles fine on FreeBSD 13. The test
  suite passes.
diff: #if !defined(_WIN32)
  #include <net/if.h>
  -#if defined(__APPLE__)
  +#if defined(__APPLE__) || defined(__FreeBSD__)
  #include <ifaddrs.h>
  #include <net/if_dl.h>
  @@ -147,7 +147,7 @@ namespace vcpkg
  }
  }
  }
  -#elif defined(__linux__) || defined(__APPLE__)
  +#elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__)
  // The getifaddrs(ifaddrs** ifap) function creates a linked list of structures
  // describing the network interfaces of the local system, and stores
  // the address of the first item of the list in *ifap.
  @@ -188,7 +188,7 @@ namespace vcpkg
  auto address = reinterpret_cast<sockaddr_ll*>(interface->ifa_addr);
  if (address->sll_halen != MAC_BYTES_LENGTH) continue;
  auto mac_bytes = Span<char>(reinterpret_cast<char*>(address->sll_addr), MAC_BYTES_LENGTH);
  -#elif defined(__APPLE__)
  +#elif defined(__APPLE__) || defined(__FreeBSD__)
  auto address = reinterpret_cast<sockaddr_dl*>(interface->ifa_addr);
  if (address->sdl_alen != MAC_BYTES_LENGTH) continue;
  // The macro LLADDR() returns the start of the link-layer network address.
  