Describe the bug
In ubuntu (16.04 14.04）and many other Linux distribution, "sh" links to /bin/sh not /bin/bash. build-thirdparty.sh use source command which only exists in /bin/bash not /bin/sh.
Run build-thirdparty.sh by sh fails and downlaod-thirdparty.sh:65 use sh to run download-thirdparty.sh.
Because both first line of download-thirdpaty.sh and build-thirdparty.sh is "#!/bin/bash", the bash scripts can run directly without “sh".

To Reproduce
Steps to reproduce the behavior:

1. sh ./thirdparty/build-thirdparty.sh
2. See error:
   thirdparty/build-thirdparty.sh: 41: thirdparty/build-thirdparty.sh: source: not found

Expected behavior
build third-party source

Screenshots

Desktop (please complete the following information):

• OS: Ubuntu
• Version 16.04

Additional context
Add any other context about the problem here.