build: use main package instead of main.go

[knqyf263]

Description

Our release binaries don't include the main module information now, and our gobinary analyzer doesn't work on them.

$ docker run --rm -it --entrypoint "sh" ghcr.io/aquasecurity/trivy:0.51.2 -c "apk add go && go version -m /usr/local/bin/trivy" | grep "/usr/local/bin/trivy" -A 5
/usr/local/bin/trivy: go1.22.3
        path    command-line-arguments
        dep     cloud.google.com/go     v0.112.1        h1:uJSeirPke5UNZHIb4SxfZklVSiWWVqW4oXlETwZziwM=
        dep     cloud.google.com/go/compute/metadata    v0.2.3  h1:mg4jlk7mCAj6xXp9UJ4fjI9VUI5rubuGBW5aJ7UnBMY=
        dep     cloud.google.com/go/iam v1.1.6  h1:bEa06k05IO4f4uJonbB5iAgKTPpABy1ayxaIZV/GHVc=
        dep     cloud.google.com/go/storage     v1.39.1 h1:MvraqHKhogCOTXTlct/9C3K3+Uy2jBmFYb3/Sp6dVtY=

A binary built by Mage includes it.

$ mage build && go version -m ./trivy | head -n 5
./trivy: go1.22.3
        path    github.com/aquasecurity/trivy/cmd/trivy
        mod     github.com/aquasecurity/trivy   (devel)
        dep     cloud.google.com/go     v0.112.1        h1:uJSeirPke5UNZHIb4SxfZklVSiWWVqW4oXlETwZziwM=
        dep     cloud.google.com/go/compute/metadata    v0.2.3  h1:mg4jlk7mCAj6xXp9UJ4fjI9VUI5rubuGBW5aJ7UnBMY=

This is because GoRelease uses main.go, cmd/trivy/main.go, while Mage uses the main package, ./cmd/trivy. This PR fixes it.

Before

$ goreleaser build -f goreleaser.yml --skip-validate --id build-macos --clean && go version -m dist/build-macos_darwin_amd64_v1/trivy | head -n 5
dist/build-macos_darwin_amd64_v1/trivy: go1.22.3
        path    command-line-arguments
        dep     cloud.google.com/go     v0.112.1        h1:uJSeirPke5UNZHIb4SxfZklVSiWWVqW4oXlETwZziwM=
        dep     cloud.google.com/go/compute/metadata    v0.2.3  h1:mg4jlk7mCAj6xXp9UJ4fjI9VUI5rubuGBW5aJ7UnBMY=
        dep     cloud.google.com/go/iam v1.1.6  h1:bEa06k05IO4f4uJonbB5iAgKTPpABy1ayxaIZV/GHVc=

After

$ goreleaser build -f goreleaser.yml --skip-validate --id build-macos --clean && go version -m dist/build-macos_darwin_amd64_v1/trivy | head -n 5
dist/build-macos_darwin_amd64_v1/trivy: go1.22.3
        path    github.com/aquasecurity/trivy/cmd/trivy
        mod     github.com/aquasecurity/trivy   (devel)
        dep     cloud.google.com/go     v0.112.1        h1:uJSeirPke5UNZHIb4SxfZklVSiWWVqW4oXlETwZziwM=
        dep     cloud.google.com/go/compute/metadata    v0.2.3  h1:mg4jlk7mCAj6xXp9UJ4fjI9VUI5rubuGBW5aJ7UnBMY=

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options)
• I've included a "before" and "after" example to the description (if the PR is a user interface change).

[knqyf263]

I confirmed it's fixed now.

$ docker run --rm -it --entrypoint "sh" ghcr.io/aquasecurity/trivy:0.51.4 -c "apk add go && go version -m /usr/local/bin/trivy" | grep "/usr/local/bin/trivy" -A 5

/usr/local/bin/trivy: go1.22.3
        path    github.com/aquasecurity/trivy/cmd/trivy
        mod     github.com/aquasecurity/trivy   (devel)
        dep     cloud.google.com/go     v0.112.1        h1:uJSeirPke5UNZHIb4SxfZklVSiWWVqW4oXlETwZziwM=
        dep     cloud.google.com/go/compute/metadata    v0.2.3  h1:mg4jlk7mCAj6xXp9UJ4fjI9VUI5rubuGBW5aJ7UnBMY=
        dep     cloud.google.com/go/iam v1.1.6  h1:bEa06k05IO4f4uJonbB5iAgKTPpABy1ayxaIZV/GHVc=