chore: fix lint error

[MaineK00n]

What did you implement:

Fixed a lint error caused by revive and golangci-lint.
Reviewed the tasks in GNUmakefile and changed (pre)test to be done in all instead of build.

Also, Trivy binary is now included with fvuls image.

$ docker run -it --rm vuls/fvuls /bin/sh
/vuls # ls /usr/local/bin
future-vuls    trivy          trivy-to-vuls  vuls

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

$ make test
$ make golangci

Checklist:

You don't have to satisfy all of the following.

• Write tests
• Write documentation
• Check that there aren't other open pull requests for the same issue/feature
• Format your source code by make fmt
• Pass the test by make test
• Provide verification config / commands
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES

Reference