Fix error message for incorrect platform used

[singhd789]

Describe your changes

If an incorrect platform was passed with the fre make commands, there was a very informative error raised. This fixes the error message to basically say "the platform passed doesn't exists in the platforms.yaml"

Issue ticket number and link (if applicable)

Checklist before requesting a review

• I ran my code
• I tried to make my code readable
• I tried to comment my code
• I wrote a new test, if applicable
• I wrote new instructions/documentation, if applicable
• I ran pytest and inspected it's output
• I ran pylint and attempted to implement some of it's feedback