Warn on unsupported operating systems

Author: sortie

configure.ac

@@ -159,3 +159,7 @@ AM_CONDITIONAL([ENABLE_LIBTLS_ONLY], [test "x$enable_libtls_only" = xyes])
 AC_REQUIRE_AUX_FILE([tap-driver.sh])
 
 AC_OUTPUT
+
+if test "$HOST_OS" = "unsupported"; then
+       AC_MSG_WARN([unsupported platform: $host_os])
+fi

m4/check-os-options.m4

@@ -132,7 +132,7 @@ char buf[1]; getentropy(buf, 1);
 		AC_SUBST([PLATFORM_LDADD], ['-ldl -lmd -lnsl -lsocket'])
 		;;
 	*)
-		HOST_OS=$host_os
+		HOST_OS=unsupported
 		HOST_ABI=elf
 		;;
 esac