Fix build on Fedora 34 / Ruby 3.0.1

Signed-off-by: François Andriot <francois.andriot@free.fr>

lib/kross/configure.in.in

@@ -43,6 +43,9 @@ if test "x$compile_kross" = "xyes" ; then
     if test "$RUBY_SERIES" -ge "19"; then
        AC_DEFINE_UNQUOTED(HAVE_RUBY_1_9, 1, [Defines if your system has Ruby 1.9.x])
     fi
+    if test "$RUBY_SERIES" -ge "30"; then
+       AC_DEFINE_UNQUOTED(HAVE_RUBY_3, 1, [Defines if your system has Ruby 3.x])
+    fi
 
     if test `${RUBY_EXECUTABLE} -r rbconfig -e "puts RbConfig::CONFIG.key?(%q(rubyhdrdir))"` = "true"; then
        RUBY_INCLUDEDIR=`${RUBY_EXECUTABLE} -r rbconfig -e "puts RbConfig::CONFIG.fetch(%q(rubyhdrdir))"`

lib/kross/ruby/rubyscript.cpp

@@ -31,7 +31,9 @@
 #include <rubysig.h>
 #include <node.h>
 #else // HAVE_RUBY_1_9
+#ifndef HAVE_RUBY_3
 #include <ruby/backward/rubysig.h>
+#endif // HAVE_RUBY_3
 #endif // HAVE_RUBY_1_9
 
 #include <main/scriptcontainer.h>