Add spec for IO.select with -INFINITY as timeout

Since `(-Float::INFINITY).infinite?` returns a truthy value, this should
probably be covered.

Author: herwinw

core/io/select_spec.rb

@@ -115,6 +115,12 @@
     -> { IO.select(nil, nil, nil, -5)}.should raise_error(ArgumentError, "time interval must not be negative")
   end
 
+  ruby_version_is "4.0" do
+    it "raises an ArgumentError when passed negative infinity as timeout" do
+      -> { IO.select(nil, nil, nil, -Float::INFINITY)}.should raise_error(ArgumentError, "time interval must not be negative")
+    end
+  end
+
   describe "returns the available descriptors when the file descriptor" do
     it "is in both read and error arrays" do
       @wr.write("foobar")