```typescript
export function applyOverrides(base: Record<string, string>, overrides: string[]): Record<string, string> {
  if (!Array.isArray(overrides)) {
    throw new Error("Invalid argument 'overrides': must be a list.");
  }

  const result = { ...base };

  for (const override of overrides) {
    const [name, value] = override.split('=');

    if (!value || name === "" || base[name] === undefined) {
      throw new Error(`Invalid override: ${override}.`);
    }

    result[name] = value;
  }

  return result;
}
```