proc: implement follow exec mode on Windows

Author: aarzilli

Documentation/backend_test_health.md

@@ -5,14 +5,16 @@ Tests skipped by each supported backend:
 	* 3 not implemented
 * arm64 skipped = 1
 	* 1 broken - global variable symbolication
-* darwin skipped = 1
+* darwin skipped = 3
+	* 2 follow exec not implemented on macOS
 	* 1 waitfor implementation is delegated to debugserver
 * darwin/arm64 skipped = 2
 	* 2 broken - cgo stacktraces
 * darwin/lldb skipped = 1
 	* 1 upstream issue
-* freebsd skipped = 6
+* freebsd skipped = 8
 	* 2 flaky
+	* 2 follow exec not implemented on freebsd
 	* 4 not implemented
 * linux/386/pie skipped = 1
 	* 1 broken

pkg/proc/native/followexec_other.go

@@ -1,5 +1,5 @@
-//go:build !linux
-// +build !linux
+//go:build !linux && !windows
+// +build !linux,!windows
 
 package native
 
@@ -9,3 +9,7 @@ import "errors"
 func (*nativeProcess) FollowExec(bool) error {
 	return errors.New("follow exec not implemented")
 }
+
+func (*processGroup) detachChild(*nativeProcess) error {
+	panic("not implemented")
+}

pkg/proc/native/proc.go

@@ -247,7 +247,7 @@ func (procgrp *processGroup) add(p *nativeProcess, pid int, currentThread proc.T
 	if tgt == nil {
 		i := len(procgrp.procs)
 		procgrp.procs = append(procgrp.procs, p)
-		procgrp.Detach(p.pid, false)
+		procgrp.detachChild(p)
 		if i == len(procgrp.procs)-1 {
 			procgrp.procs = procgrp.procs[:i]
 		}
@@ -262,7 +262,7 @@ func (procgrp *processGroup) add(p *nativeProcess, pid int, currentThread proc.T
 }
 
 func (procgrp *processGroup) ContinueOnce(cctx *proc.ContinueOnceContext) (proc.Thread, proc.StopReason, error) {
-	if len(procgrp.procs) != 1 && runtime.GOOS != "linux" {
+	if len(procgrp.procs) != 1 && runtime.GOOS != "linux" && runtime.GOOS != "windows" {
 		panic("not implemented")
 	}
 	if procgrp.numValid() == 0 {

pkg/proc/native/proc_linux.go

@@ -845,6 +845,10 @@ func stop1(cctx *proc.ContinueOnceContext, dbp *nativeProcess, trapthread *nativ
 	return err1
 }
 
+func (procgrp *processGroup) detachChild(dbp *nativeProcess) error {
+	return procgrp.Detach(dbp.pid, false)
+}
+
 func (dbp *nativeProcess) detach(kill bool) error {
 	for threadID := range dbp.threads {
 		err := ptraceDetach(threadID, 0)