wgengine/magicsock: make debugUseDerpRoute an opt.Bool.
Can still be constant, just needs the extra methods.
Fixes
package magicsock
+import "tailscale.com/types/opt"
+
// All knobs are disabled on iOS.
// Further, they're const, so the toolchain can produce smaller binaries.
const (
debugDisco = false
debugOmitLocalAddresses = false
debugUseDerpRouteEnv = ""
- debugUseDerpRoute = false
+ debugUseDerpRoute opt.Bool = ""
logDerpVerbose = false
debugReSTUNStopOnIdle = false
debugAlwaysDERP = false
