cmd/cgo: Add all gccgo GOARCH values to size maps.
cmd/cgo: Add all gccgo GOARCH values to size maps.

GCC PR go/65353.

R=iant
CC=gofrontend-dev
https://golang.org/cl/210610043

golang/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,golang/gofrontend,anlhord/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,golang/gofrontend,anlhord/gofrontend,anlhord/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,anlhord/gofrontend,golang/gofrontend,qskycolor/gofrontend