cmd/8l: add support for dragonfly/386

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/13328045

src/cmd/8l/asm.c

@@ -847,6 +847,7 @@ asmb(void)
 	case Hfreebsd:
 	case Hnetbsd:
 	case Hopenbsd:
+	case Hdragonfly:
 		asmbelf(symo);
 		break;
 	case Hwindows:

src/cmd/8l/obj.c

@@ -53,6 +53,7 @@ Header headers[] = {
 	"msdoscom", Hmsdoscom,
 	"msdosexe", Hmsdosexe,
 	"darwin", Hdarwin,
+	"dragonfly", Hdragonfly,
 	"linux", Hlinux,
 	"freebsd", Hfreebsd,
 	"netbsd", Hnetbsd,
@@ -69,6 +70,7 @@ Header headers[] = {
  *	-Hmsdoscom -Tx -Rx			is MS-DOS .COM
  *	-Hmsdosexe -Tx -Rx			is fake MS-DOS .EXE
  *	-Hdarwin -Tx -Rx			is Apple Mach-O
+ *	-Hdragonfly -Tx -Rx			is DragonFly ELF32
  *	-Hlinux -Tx -Rx				is Linux ELF32
  *	-Hfreebsd -Tx -Rx			is FreeBSD ELF32
  *	-Hnetbsd -Tx -Rx			is NetBSD ELF32
@@ -153,6 +155,7 @@ main(int argc, char *argv[])
 			sysfatal("cannot use -linkmode=external with -H %s", headstr(HEADTYPE));
 		break;
 	case Hdarwin:
+	case Hdragonfly:
 	case Hfreebsd:
 	case Hlinux:
 	case Hnetbsd:
@@ -242,6 +245,7 @@ main(int argc, char *argv[])
 	case Hfreebsd:
 	case Hnetbsd:
 	case Hopenbsd:
+	case Hdragonfly:
 		/*
 		 * ELF uses TLS offsets negative from %gs.
 		 * Translate 0(GS) and 4(GS) into -8(GS) and -4(GS).

src/cmd/ld/doc.go

@@ -33,7 +33,7 @@ Options new in this version:
 		linker. This flag cannot be used when $GOOS is windows.
 	-H darwin     (only in 6l/8l)
 		Write Apple Mach-O binaries (default when $GOOS is darwin)
-	-H dragonfly  (only in 6l)
+	-H dragonfly  (only in 6l/8l)
 		Write DragonFly ELF binaries (default when $GOOS is dragonfly)
 	-H linux
 		Write Linux ELF binaries (default when $GOOS is linux)