GetFunctionsCoreToolsPath fails to find Azure Function Core Tools on Mac

[VasuBhog]

On Mac: Azure Function Core tools is (most likely) installed via Brew.

Therefore the GetFunctionCoreTools will fail on finding the core tools in node modules (shown below):

System.IO.FileNotFoundException : Azure Function Core Tools not found at /usr/local/lib/node_modules/azure-functions-core-tools/bin/func.

We should also check brew for Mac OS development so that it can properly find the function core tools path and not have to hardcode the path.

Workaround:

• comment out GetFunctionsCoreToolsPath and set this line to where the location of func is (use where func in the terminal to find the location).

[lucyzhang929]

Fixed here: #533