net-im/gotosocial: update to 0.7.0

Enable on aarch64, i386, and armv7 after successful build test.

Use go.mk framework to build:

• use go:modules
• set GO_BUILDFLAGS
• set GO_TARGET
• add CGO_ENABLED=0
• remove binary from do-install
• move rest of do-install to post-install

Changelog: https://github.com/superseriousbusiness/gotosocial/releases/tag/v0.7.0

PR: 269632
Approved by: flo (mentor)
Differential Revision: https://reviews.freebsd.org/D38688