run.bash: fix build on netbsd builders.

LGTM=bradfitz
R=golang-codereviews, bradfitz, dave
CC=golang-codereviews
https://golang.org/cl/88000044

src/run.bash

@@ -132,7 +132,7 @@ dragonfly-386 | dragonfly-amd64 | freebsd-386 | freebsd-amd64 | linux-386 | linu
 	go test -ldflags '-linkmode=auto' ../testtls || exit 1
 	go test -ldflags '-linkmode=external' ../testtls || exit 1
 	
-	case "$GOHOSTOS-GOARCH" in
+	case "$GOHOSTOS-$GOARCH" in
 	netbsd-386 | netbsd-amd64) ;; # no static linking
 	*)
 		go test -ldflags '-linkmode=external -extldflags "-static -pthread"' ../testtls || exit 1