Build go binaries as PIE

[freebsd_igalic.co]

Summary

We adapt GO_BUILDFLAGS to change the default build mode for executables from exe to pie.
This allows executables build with the go toolchain now to run on systems with PIE, ASLR or WX enabled.

Or, failing so, at least have the appropriate ELF section embedded which elfctl can use to disable what doesn't work.

See https://github.com/golang/go/issues/48112 for reference.

[freebsd_igalic.co]

modify net/syncthing build to build the binaries as pie

[orangewinds_gmail.com]

Hello! I do not see GOFLAGS in the Makefile anymore (where -buildmode=pie is inserted here). Does that mean this is already implemented elsewhere, or just that how this would be done on FBSD 13/ports has changed? We are currently building Syncthing with Go 1.18, so I think all parts of this are otherwise ready. Thank you!

[freebsd_igalic.co]

Given the fixes the go toolchain has received, this blanket fix should no longer be necessary