cmd/5l: make 5l work on openbsd

Change-Id: If58ea50fbf321ae943d0890a40e0552e7bc19709
Reviewed-on: https://go-review.googlesource.com/2080Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/5l/obj.go

@@ -74,7 +74,7 @@ func linkarchinit() {
 
 	ld.Thearch.Linuxdynld = "/lib/ld-linux.so.3" // 2 for OABI, 3 for EABI
 	ld.Thearch.Freebsddynld = "/usr/libexec/ld-elf.so.1"
-	ld.Thearch.Openbsddynld = "XXX"
+	ld.Thearch.Openbsddynld = "/usr/libexec/ld.so"
 	ld.Thearch.Netbsddynld = "/libexec/ld.elf_so"
 	ld.Thearch.Dragonflydynld = "XXX"
 	ld.Thearch.Solarisdynld = "XXX"
@@ -124,7 +124,8 @@ func archinit() {
 
 	case ld.Hlinux, /* arm elf */
 		ld.Hfreebsd,
-		ld.Hnetbsd:
+		ld.Hnetbsd,
+		ld.Hopenbsd:
 		ld.Debug['d'] = 0
 		// with dynamic linking
 		ld.Elfinit()