build: Enable BSD symbols for Haiku

Tell Haiku to provide various BSD functions by setting BSD_SOURCE
and linking libbsd.
Signed-off-by: NDavid Carlier <devnexen@gmail.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 20200703145614.16684-2-peter.maydell@linaro.org
[PMM: expanded commit message]
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

configure

@@ -904,8 +904,8 @@ SunOS)
 ;;
 Haiku)
   haiku="yes"
-  QEMU_CFLAGS="-DB_USE_POSITIVE_POSIX_ERRORS $QEMU_CFLAGS"
-  LIBS="-lposix_error_mapper -lnetwork $LIBS"
+  QEMU_CFLAGS="-DB_USE_POSITIVE_POSIX_ERRORS -DBSD_SOURCE $QEMU_CFLAGS"
+  LIBS="-lposix_error_mapper -lnetwork -lbsd $LIBS"
 ;;
 Linux)
   audio_drv_list="try-pa oss"