cmd/link: add support for telemetry

Add counters for invocations and provided flag names.

For #58894

Change-Id: Ibd4eeca905d277879b601d95bab524fbced6a98b
Reviewed-on: https://go-review.googlesource.com/c/go/+/584276
Reviewed-by: Than McIntosh <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: matloob

src/cmd/link/internal/ld/main.go

@@ -36,6 +36,7 @@ import (
 	"cmd/internal/objabi"
 	"cmd/internal/quoted"
 	"cmd/internal/sys"
+	"cmd/internal/telemetry"
 	"cmd/link/internal/benchmark"
 	"flag"
 	"internal/buildcfg"
@@ -155,6 +156,8 @@ func (t *ternaryFlag) IsBoolFlag() bool { return true } // parse like a boolean
 func Main(arch *sys.Arch, theArch Arch) {
 	log.SetPrefix("link: ")
 	log.SetFlags(0)
+	telemetry.Start()
+	telemetry.Inc("link/invocations")
 
 	thearch = theArch
 	ctxt := linknew(arch)
@@ -200,6 +203,7 @@ func Main(arch *sys.Arch, theArch Arch) {
 	objabi.Flagfn1("importcfg", "read import configuration from `file`", ctxt.readImportCfg)
 
 	objabi.Flagparse(usage)
+	telemetry.CountFlags("link/flag:", *flag.CommandLine)
 
 	if ctxt.Debugvlog > 0 {
 		// dump symbol info on crash