Added shebang to build script

[TorbenKoehn]

This avoids build problems when you're using another default shell like zsh.

[msftclas]

Hi @TorbenKoehn, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

This seems like a small (but important) contribution, so no Contribution License Agreement is required at this point. Real humans will now evaluate your PR.

TTYL, MSBOT;

[jianchun]

Thanks for the change! Should we use /bin/bash? The script used to have problems with /bin/sh. I think previously we had trouble with the license header checker for this change. Seems that problem is gone. @dilijev

[TorbenKoehn]

Absolutely. Changed it.

[obastemur]

Should we use /bin/bash? The script used to have problems with /bin/sh.

bin/sh forces POSIX. So, the differences. However makes sure the experience due to strict bacward compatibility. On the other hand, for the range of platforms we target, 'bash' makes more sense for us.

[obastemur]

LGTM

[jianchun]

Thanks @TorbenKoehn, and @obastemur for confirmation. I'll merge this.

[dilijev]

@jianchun yes, last time this came up @obastemur and I fixed the copyright check to support shebangs as the first line of the file before the required copyright header.

[jianchun]

@dilijev Thanks for confirm!

[dilijev]

For reference, that logic is here: https://github.com/Microsoft/ChakraCore/blob/master/jenkins/check_copyright.py#L46