cmd/link: add -e (no limit on errors) flag

The compiler and assembler have a -e flag that disables the limit
on the number of errors before the build fails. This flag is useful
for debugging, the linker should have it too.

Change-Id: I892cfd6ee1519e9e86261af7d05e1af2ded21684
Reviewed-on: https://go-review.googlesource.com/c/go/+/646435
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/link/doc.go

@@ -72,6 +72,8 @@ Flags:
 		system tools now assume the presence of the header.
 	-dumpdep
 		Dump symbol dependency graph.
+	-e
+		No limit on number of errors reported.
 	-extar ar
 		Set the external archive program (default "ar").
 		Used only for -buildmode=c-archive.

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

@@ -108,6 +108,7 @@ var (
 	flagEntrySymbol   = flag.String("E", "", "set `entry` symbol name")
 	flagPruneWeakMap  = flag.Bool("pruneweakmap", true, "prune weak mapinit refs")
 	flagRandLayout    = flag.Int64("randlayout", 0, "randomize function layout")
+	flagAllErrors     = flag.Bool("e", false, "no limit on number of errors reported")
 	cpuprofile        = flag.String("cpuprofile", "", "write cpu profile to `file`")
 	memprofile        = flag.String("memprofile", "", "write memory profile to `file`")
 	memprofilerate    = flag.Int64("memprofilerate", 0, "set runtime.MemProfileRate to `rate`")

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

@@ -48,7 +48,7 @@ func afterErrorAction() {
 	if *flagH {
 		panic("error")
 	}
-	if nerrors > 20 {
+	if nerrors > 20 && !*flagAllErrors {
 		Exitf("too many errors")
 	}
 }