有没有办法在 ubuntu 18.04 上安装 gcc 4.9？我试过
sudo add-apt-repository ppa:ubuntu-toolchain-r/ppa
sudo apt-get update
sudo apt-get install gcc-4.9 g++-4.9
但我得到：
Package g++-4.9 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
我需要这个版本来用狙击手运行一些模拟。有没有办法做到这一点，或者我必须用 ubuntu 16.04 制作一个虚拟机？