详细错误：
/usr/bin/ld: /tmp/ccZUXOcx.o: in function `AppLauncher::AppLauncher()':
ProductStarter.cpp:(.text._ZN11AppLauncherC2Ev[_ZN11AppLauncherC5Ev]+0xf): undefined reference to `vtable for AppLauncher'
/usr/bin/ld: /tmp/ccgYBOTx.o:(.data.rel.ro._ZTI15ProductLauncher[_ZTI15ProductLauncher]+0x10): undefined reference to `typeinfo for AppLauncher'
collect2: error: ld returned 1 exit status
咱玩C++也有点年头了……其实这个错误是吾自己解决的。具体参考：
https://blog.csdn.net/quantum7/article/details/88085619
吾在定义的时候也想到了这一点，只是觉得不是必须的。结果……
