Set CGO_CFLAGS, CGO_CXXFLAGS and CGO_LDFLAGS

[bbhtt]

Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Suggestion

These environment variables should be set to:

CGO_CFLAGS -> CFLAGS
CGO_CXXFLAGS -> CXXFLAGS
CGO_LDFLAGS -> LDFLAGS

https://pkg.go.dev/cmd/cgo