The buildvar flag doesn't support values with commas

[rocketeerbkw]

Describe the bug
Attempting to use a comma as part of a buildvar value throws Error: Malformed build variable entry (expects KEY=VALUE).

To Reproduce
Steps to reproduce the behavior:
Run lagoon deploy latest -p example -e main --buildvar LAGOON_SERVICE_TYPES="cli:cli,php:php"

Expected behavior
Since some of the Lagoon env vars require the use of commas, they should not throw errors when used.

Additional context
The buildvar flag uses a StringSlice library type to:

take comma-separated value as arguments and split them accordingly

So both of these are valid: --buildvar KEY1=v --buildvar KEY2=v and --buildvar KEY1=v,KEY2=v. There are some issues in the pflag github that suggest this was fixed, so it could also be an issue with our implementation of buildVarsToMap?