go/build: enable cgo by default on solaris/amd64

Change-Id: I0110b01fe4c64851ac2cfb5a92c31ce156831bc8
Reviewed-on: https://go-review.googlesource.com/8265Reviewed-by: Minux Ma <minux@golang.org>

src/go/build/build.go

@@ -275,6 +275,7 @@ var cgoEnabled = map[string]bool{
 	"netbsd/arm":      true,
 	"openbsd/386":     true,
 	"openbsd/amd64":   true,
+	"solaris/amd64":   true,
 	"windows/386":     true,
 	"windows/amd64":   true,
 }