[swift-users] SwiftPM on Linux Failed

[adelzhang at qq.com]

Hi, everyone.

Installing swift on linux is not that easy. Following  
https://swift.org/getting-started/#using-the-package-manager instruction,  
but `swift build` failed:

```
error: manifest parse error(s):
/home/vagrant/hello/Package.swift:4:8: error: no such module  
'PackageDescription'
import PackageDescription
        ^
```

I installed Swift 4.0

```
$swift version
Swift version 4.0-dev (LLVM 2dedb62a0b, Clang b9d76a314c, Swift 0899bd328a)
Target: x86_64-unknown-linux-gnu
```

Ubuntu 14.04 is running on VirtualBox using vagrant.

```
$lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 14.04.5 LTS
Release:	14.04
Codename:	trusty
```

Does someone happen to know the work-around?

-- 
Regards

adelzhang