Fix for centos and mac

[xaoseric]

Added fetch-params-mac.sh for mac users, and changed shasum to sha256sum redhat based os fix

[daira]

Changing to sha256sum will fix some platforms and break others (see #776 and #1053 (comment)). We should instead try sha256sum and fall back to shasum -a 256 (as @ebfull originally suggested in #776 (comment) ).

[xaoseric]

@daira the fetch-params-mac.sh file solves that issue as Ubuntu and Debian already have sha256sum support. 8a8fdeb

[xaoseric]

@daira i did try playing around with your suggestion, couldn't get it to work though, so if you want to take a look at it, feel free

[daira]

SHA256CMD="$(command -v sha256sum || echo shasum)"
SHA256ARGS="$(command -v sha256sum >/dev/null || echo '-a 256')"
"$SHA256CMD" $SHA256ARGS filename

(It's harder with the correct quoting; if we assumed that the path to sha256sum had no special characters then it would be simpler.)

[zkbot]

☔ The latest upstream changes (presumably a885ee4) made this pull request unmergeable. Please resolve the merge conflicts.

[daira]

Superceded by #1628.