The new 'toolchain' directive in go.mod can sometimes force
the use of an upstream toolchain against our wishes. Concurrently,
some of our dependencies have added the 'toolchain' directive, which
transitively adds it to our own go.mod. Force all uses of gocross to
ignore that directive and stick to our customized toolchain.
Updates #cleanup
Signed-off-by: David Anderson <danderson@tailscale.com>
It's used to control various opt-in functionality for the macOS and iOS
apps, and was lost in the migration to gocross.
Updates tailscale/tailscale#7769
Signed-off-by: Mihai Parparita <mihai@tailscale.com>
Xcode changed how/what data it exports to build steps at some point
recently, so our old way of figuring out the minimum support version
for clang stopped working.
Updates tailscale/corp#4095
Signed-off-by: David Anderson <danderson@tailscale.com>
