Clone process.env to ensure source of truth is not changed

Part of #128745

src/vs/platform/externalTerminal/node/externalTerminalService.ts

@@ -312,7 +312,7 @@ export class LinuxExternalTerminalService extends ExternalTerminalService implem
 }
 
 function getSanitizedEnvironment(process: NodeJS.Process) {
-	const env = process.env;
+	const env = { ...process.env };
 	// Refs https://github.com/microsoft/vscode/issues/128745#issuecomment-885981676
 	sanitizeProcessEnvironment(env, 'VSCODE_BROWSER_CODE_LOADING');
 	return env;