Gremlins should use a separate temporary directory as Go build cache

[k3rn31]

As suggeste by @hknutzen in #178, Gremlins should use a separate temporary directory as Go build cache. This should be removed after each run of gremlins.
This should be done to avoid an unbound growth of the default cache directory.

https://pkg.go.dev/cmd/go#hdr-Build_and_test_caching

The go command caches build outputs for reuse in future builds. The default location for cache data is a subdirectory named go-build in the standard user cache directory for the current operating system. Setting the GOCACHE environment variable overrides this default, and running 'go env GOCACHE' prints the current cache directory.

[k3rn31]

@giorgiaroccetti whould you like to start looking into this?