test(agentcompat): add process supervision harness

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

integration/agentcompat/internal/workspace/build.go

@@ -0,0 +1,56 @@
+//go:build linux
+
+package workspace
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+)
+
+type BuildSpec struct {
+	Name      string
+	SourceDir string
+	Package   string
+	Tags      []string
+	Ldflags   []string
+	Env       []string
+}
+
+func (workspace *Workspace) Build(ctx context.Context, spec BuildSpec) (string, error) {
+	workspace.closeMu.Lock()
+	defer workspace.closeMu.Unlock()
+	if err := workspace.requireOpen(); err != nil {
+		return "", err
+	}
+	if spec.SourceDir == "" || spec.Package == "" {
+		return "", errors.New("build source and package are required")
+	}
+	if err := validateLeafName(spec.Name); err != nil {
+		return "", err
+	}
+	binaryPath := filepath.Join(workspace.binDir, spec.Name)
+	arguments := []string{"build", "-mod=readonly", "-o", binaryPath}
+	if len(spec.Tags) > 0 {
+		arguments = append(arguments, "-tags", strings.Join(spec.Tags, ","))
+	}
+	if len(spec.Ldflags) > 0 {
+		arguments = append(arguments, "-ldflags", strings.Join(spec.Ldflags, " "))
+	}
+	arguments = append(arguments, spec.Package)
+	command := exec.CommandContext(ctx, "go", arguments...)
+	command.Dir = spec.SourceDir
+	command.Env = spec.Env
+	if spec.Env == nil {
+		command.Env = os.Environ()
+	}
+	output, err := command.CombinedOutput()
+	if err != nil {
+		return "", fmt.Errorf("build %s: %w: %s", spec.Name, err, output)
+	}
+	return binaryPath, nil
+}