sys/generated: don't do lazy initialization of all targets

Currently registration of targets calls targets.Get which does slow lazy initialization.
This adds several seconds to start of every binary and test. Don't do that.

Author: dvyukov

sys/generated/generated.go

@@ -24,7 +24,8 @@ type Desc struct {
 }
 
 func Register(os, arch, revision string, init func(*prog.Target), files embed.FS) {
-	sysTarget := targets.Get(os, arch)
+	// Does not call targets.Get b/c it does slow lazy initialization of targets.
+	sysTarget := targets.List[os][arch]
 	target := &prog.Target{
 		OS:         os,
 		Arch:       arch,