main.star: use v7l suffix for netbsd-arm builder

It was updated to target GOARM=7 because it can't work with GOARM=6.

For golang/go#63698.

Change-Id: I164a49d4a2bf6f680e4a980e90f6e2968f1906a7
Reviewed-on: https://go-review.googlesource.com/c/build/+/623015
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

main.star

@@ -1263,7 +1263,8 @@ def dimensions_of(host_type):
     if goos == "darwin":
         cipd_platform = "mac-" + goarch  # GOHOSTOS=darwin is written as "mac".
     elif goarch == "arm":
-        cipd_platform = goos + "-armv6l"  # GOHOSTARCH=arm is written as "armv6l".
+        suffix = "v7l" if goos == "netbsd" else "v6l"
+        cipd_platform = goos + "-arm" + suffix  # GOHOSTARCH=arm is written as "arm{suffix}".
     else:
         cipd_platform = host