Use same value for host_os as meson for GNU/Hurd.

Signed-off-by: Damien Zammit <damien@zamaudio.com>
---
 configure | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/configure b/configure
index 4b61fd3bbf..fae4d06352 100755
--- a/configure
+++ b/configure
@@ -372,6 +372,8 @@ elif check_define __APPLE__; then
 elif check_define EMSCRIPTEN ; then
   host_os=emscripten
   cross_compile="yes"
+elif check_define __GNU__; then
+  host_os=gnu
 else
   # This is a fatal error, but don't report it yet, because we
   # might be going to just print the --help text, or it might
-- 
2.51.0