have to quote the AC_MSG_ERROR else the exit code is screwed up
diff --git a/m4/gl.m4 b/m4/gl.m4
index 182544d..c117cb5 100644
--- a/m4/gl.m4
+++ b/m4/gl.m4
@@ -34,7 +34,7 @@ else
fi
CPPFLAGS="$GL_CFLAGS"
-AC_CHECK_HEADER([GL/gl.h], [], [AC_MSG_ERROR(GL/gl.h is needed, please specify its location with --with-gl-inc. If this still fails, please contact mmagallo@debian.org, include the string FTGL somewhere in the subject line and provide a copy of the config.log file that was left behind.)])
+AC_CHECK_HEADER([GL/gl.h], [], [AC_MSG_ERROR([GL/gl.h is needed, please specify its location with --with-gl-inc. If this still fails, please contact mmagallo@debian.org, include the string FTGL somewhere in the subject line and provide a copy of the config.log file that was left behind.])])
AC_MSG_CHECKING([for GL library])
if test "x$with_gl_lib" != "x" ; then