Use first if multiple files returned by where.exe

[edcucerzan]

What I did

I added code for when "where.exe" finds multiple solc executables. Previously this would cause the solc compiler to be not found when trying to compile a file. Now only the first line of output from where.exe is kept and everything works as expected.

Related issue: #

How I did it

How to verify it

Checklist

• [x] I have confirmed that my PR passes all linting checks
• [ ] I have included test cases
• [ ] I have updated the documentation (README.md)
• [ ] I have added an entry to the changelog

[antazoey]

Outdated- we changed to shutil.which()