add execute option to run-fremake command

[rem1776]

Is your feature request related to a problem? Please describe.
By default the run-fremake sub command always runs all the created scripts and compiles the code, which differs from bronx fremake and makes it harder to test.

Describe the solution you'd like
Don't run the compilation script by default and instead add a --execute/-e option to do the build if given.

Describe alternatives you've considered
Could also keep current behavior and compile by default, with an --no-execute option instead.