Add Homebrew path for Apple Silicon

[indiependente]

Issue

When executed as a service on macOS on an Apple Silicon machine, the script is not able to find the brew binary due to it being located under /opt/homebrew/bin/.

Proof of this is visible in the /tmp/homebrew.mxcl.aws-rotate-iam-keys.log log file:

➜  ~ cat /tmp/homebrew.mxcl.aws-rotate-iam-keys.log
GNU's enhanced getopt is required to run this script
You can usually find this in the util-linux package
On MacOS see homebrew's package: http://brewformulas.org/Gnu-getopt
For anyone else, build from source: http://frodo.looijaard.name/project/getopt

The output can be misleading because it fails on the first part of the if condition where it tries to identify the brew binary but fails.

Hence the script won't work if scheduled as a service.

Solution

Adding the Apple Silicon Homebrew binary path to the Plist file in the Environment variables section fixes the problem.

[mmrwoods]

Fixed by #76