Build: Do not omit first argument to m4_warn()

It seems that contrary to what the documentation says, leaving
the category argument to m4_warn() empty is not allowed. Use
the "unsupported" category for lack of a better choice.

diff --git a/configure.ac b/configure.ac
index dc4771e7a9797fbc6ed08337ee214c96b22937ed..173f34444b467f7c260a994ab719b95343581e97 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -332,7 +332,7 @@ sr_cxx_missing=
 # Check if the C++ compiler supports the C++11 standard.
 m4_ifdef([AX_CXX_COMPILE_STDCXX_11],
        [AX_CXX_COMPILE_STDCXX_11(, [optional])],
-       [m4_warn(, [[Missing macro AX_CXX_COMPILE_STDCXX_11: no C++11 check possible]])])
+       [m4_warn([unsupported], [Missing macro AX_CXX_COMPILE_STDCXX_11: no C++11 check possible])])
 test "x$HAVE_CXX11" = x1 || sr_cxx_missing="$sr_cxx_missing C++11"
 
 # The C++ bindings need glibmm.
@@ -391,7 +391,7 @@ PKG_CHECK_EXISTS([pygobject-3.0 < 3.7.91],
 HAVE_PYMOD_SETUPTOOLS=yes
 m4_ifdef([AX_PYTHON_MODULE],
        [AX_PYTHON_MODULE([setuptools])],
-       [m4_warn(, [[Missing macro AX_PYTHON_MODULE: no setuptools check]])])
+       [m4_warn([unsupported], [Missing macro AX_PYTHON_MODULE: no setuptools check])])
 test "x$HAVE_PYMOD_SETUPTOOLS" = xyes \
        || sr_python_missing="$sr_python_missing Setuptools"