build: apply the Console subsystem for Debug builds

If no subsystem is specified, then the resulted binary doesn't
constitute as a valid binary Win32 executable. Hence the need to specify
a subsystem for debug builds too. The `.Console` subsystem was chosen as
it allows for standard output to be logged in a console (which is quite
useful for debug builds)

build_capy.zig

@@ -176,10 +176,10 @@ pub fn runStep(step: *std.Build.Step.Compile, options: CapyRunOptions) !*std.Bui
     const optimize = step.root_module.optimize.?;
     switch (step.rootModuleTarget().os.tag) {
         .windows => {
-            switch (optimize) {
-                .Debug => {},
-                else => step.subsystem = .Windows,
-            }
+            step.subsystem = switch (optimize) {
+                .Debug => .Console,
+                else => .Windows,
+            };
         },
         .macos => {},
         .linux, .freebsd => {