build_docker.sh: bump default base image (#15432)

We now have a tailscale/alpine-base:3.19 use that as the default base image.

Updates tailscale/tailscale#15328

Signed-off-by: Irbe Krumina <irbe@tailscale.com>

build_docker.sh

@@ -16,7 +16,7 @@ eval "$(./build_dist.sh shellvars)"
 
 DEFAULT_TARGET="client"
 DEFAULT_TAGS="v${VERSION_SHORT},v${VERSION_MINOR}"
-DEFAULT_BASE="tailscale/alpine-base:3.18"
+DEFAULT_BASE="tailscale/alpine-base:3.19"
 # Set a few pre-defined OCI annotations. The source annotation is used by tools such as Renovate that scan the linked
 # Github repo to find release notes for any new image tags. Note that for official Tailscale images the default
 # annotations defined here will be overriden by release scripts that call this script.