[Agent] Windows spawning process fix

x-pack/elastic-agent/CHANGELOG.asciidoc

@@ -18,6 +18,7 @@
 - Fixed merge of config {pull}17399[17399]
 - Handle abs paths on windows correctly {pull}17461[17461]
 - Improved cancellation of agent {pull}17318[17318]
+- Fixed process spawning on Windows {pull}17751[17751]
 
 ==== New features
 

x-pack/elastic-agent/pkg/core/plugin/process/cmd.go

@@ -10,6 +10,7 @@ package process
 import (
 	"os"
 	"os/exec"
+	"path/filepath"
 
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/logger"
 )
@@ -18,6 +19,7 @@ func getCmd(logger *logger.Logger, path string, env []string, uid, gid int, arg
 	cmd := exec.Command(path, arg...)
 	cmd.Env = append(cmd.Env, os.Environ()...)
 	cmd.Env = append(cmd.Env, env...)
+	cmd.Dir = filepath.Dir(path)
 
 	return cmd
 }

x-pack/elastic-agent/pkg/core/plugin/process/process.go

@@ -191,14 +191,17 @@ func pushCredentials(w io.Writer, c *Creds) error {
 
 	credbytes, err := yaml.Marshal(c)
 	if err != nil {
-		return err
+		return errors.New(err, "decoding credentials")
 	}
 
 	_, err = w.Write(credbytes)
+	if err != nil {
+		return errors.New(err, "passing credentials failed")
+	}
 
 	// this gives beat with grpc a bit of time to spin up a goroutine and start a server.
 	// should be ok until we come up with more clever solution.
 	// Issue: https://github.com/elastic/beats/v7/issues/15634
 	<-time.After(1500 * time.Millisecond)
-	return err
+	return nil
 }