www/grafana8: fix build on riscv64, enable on armv7

Bump golang.org/x/{net,sys,sync,text,tools} dependencies
to versions new enough to build on riscv64-freebsd.

Builds fine on armv7. Only strip if requested.

Sponsored by: Berliner Linux User Group e.V.
Approved by: portmgr (build fix blanket)