debug: use lldb or gdb for cppdbg using the OS defaults

We shouldn't infer what debugger to use based on the compiler
command. Instead we use the defaults based on the OS:
https://code.visualstudio.com/docs/cpp/launch-json-reference#_mimode

src/debug/index.ts

@@ -1,3 +1,4 @@
+import * as os from "os";
 import * as vscode from "vscode";
 import * as path from "path";
 import { getMesonTargets } from "../introspection";
@@ -78,9 +79,7 @@ export class MesonDebugConfigurationProvider implements vscode.DebugConfiguratio
 
     if (type === DebuggerType.cppdbg) {
       let miMode;
-      if (
-        target.target_sources?.some((source) => source.compiler != null && ["cc", "clang"].includes(source.compiler[0]))
-      ) {
+      if (os.platform() === "darwin") {
         miMode = MIMode.lldb;
       } else {
         miMode = MIMode.gdb;