cmd/6l: support -linkshared

Change-Id: Id469165b1acd383837b1f4e1e6f961e10dfa5d61
Reviewed-on: https://go-review.googlesource.com/8332
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
diff --git a/src/cmd/internal/ld/link.go b/src/cmd/internal/ld/link.go
index 83cfe28..0eca045 100644
--- a/src/cmd/internal/ld/link.go
+++ b/src/cmd/internal/ld/link.go
@@ -114,6 +114,7 @@
 	Tlsg      *LSym
 	Libdir    []string
 	Library   []Library
+	Shlibs    []string
 	Tlsoffset int
 	Diag      func(string, ...interface{})
 	Cursym    *LSym
@@ -138,6 +139,7 @@
 	Srcref string
 	File   string
 	Pkg    string
+	Shlib  string
 }
 
 type Pcln struct {