build: disable static cgo linking test on netbsd

We get
/usr/lib/libc.a(stack_protector.o): In function `__stack_chk_fail_local':
stack_protector.c:(.text+0x158): multiple definition of `__stack_chk_fail_local'
/var/tmp/go-link-04838a/000001.o:/tmp/gobuilder/netbsd-386-minux-c7a9e9243878/go/src/pkg/runtime/cgo/gcc_386.S:41: first defined here

I am assuming this has never worked and possibly is not intended to work.
(Some systems are vehemently against static linking.)

TBR=iant
CC=golang-codereviews
https://golang.org/cl/88130046

src/run.bash

@@ -131,7 +131,14 @@ dragonfly-386 | dragonfly-amd64 | freebsd-386 | freebsd-amd64 | linux-386 | linu
 	go test -ldflags '-linkmode=external' || exit 1
 	go test -ldflags '-linkmode=auto' ../testtls || exit 1
 	go test -ldflags '-linkmode=external' ../testtls || exit 1
+	
+	case "$GOHOSTOS-GOARCH" in
+	netbsd-386 | netbsd-amd64) ;; # no static linking
+	*)
 		go test -ldflags '-linkmode=external -extldflags "-static -pthread"' ../testtls || exit 1
+		;;
+	esac
+	;;
 esac
 ) || exit $?