fix: replace util.CopyFile with custom copyFile implementation in finalize

The util package's CopyFile was removed, causing finalize to fail when copying
the pre-compiled rewrite binary to .bp/bin/rewrite.

This change:
- Adds a copyFile() method to Finalizer that preserves file permissions
- Removes dependency on the removed util package
- Updates tests to reflect the simplified file copy approach

The rewrite binary is pre-compiled by scripts/build.sh during packaging and
copied to the app's .bp/bin/ directory during finalize, making it available
for runtime configuration templating.

Integration tests pass successfully.

Author: ramonskie

src/php/finalize/finalize.go

@@ -9,7 +9,6 @@ import (
 	"github.com/cloudfoundry/libbuildpack"
 	"github.com/cloudfoundry/php-buildpack/src/php/extensions"
 	"github.com/cloudfoundry/php-buildpack/src/php/options"
-	"github.com/cloudfoundry/php-buildpack/src/php/util"
 )
 
 // Stager interface abstracts buildpack staging operations
@@ -225,17 +224,18 @@ func (f *Finalizer) CreateStartScript() error {
 		return fmt.Errorf("could not create .bp/bin directory: %v", err)
 	}
 
-	// Copy rewrite binary to .bp/bin
 	bpDir := os.Getenv("BP_DIR")
 	if bpDir == "" {
 		return fmt.Errorf("BP_DIR environment variable not set")
 	}
+
+	// Copy pre-compiled rewrite binary from bin/rewrite to .bp/bin/rewrite
 	rewriteSrc := filepath.Join(bpDir, "bin", "rewrite")
 	rewriteDst := filepath.Join(bpBinDir, "rewrite")
-	if err := util.CopyFile(rewriteSrc, rewriteDst); err != nil {
+	if err := f.copyFile(rewriteSrc, rewriteDst); err != nil {
 		return fmt.Errorf("could not copy rewrite binary: %v", err)
 	}
-	f.Log.Debug("Copied rewrite binary to .bp/bin")
+	f.Log.Debug("Copied pre-compiled rewrite binary to .bp/bin")
 
 	// Load options from options.json to determine which web server to use
 	opts, err := options.LoadOptions(bpDir, f.Stager.BuildDir(), f.Manifest, f.Log)
@@ -610,3 +610,32 @@ func (f *Finalizer) SetupProcessTypes() error {
 
 	return nil
 }
+
+func (f *Finalizer) copyFile(src, dst string) error {
+	sourceFile, err := os.Open(src)
+	if err != nil {
+		return fmt.Errorf("could not open source file: %v", err)
+	}
+	defer sourceFile.Close()
+
+	destFile, err := os.Create(dst)
+	if err != nil {
+		return fmt.Errorf("could not create destination file: %v", err)
+	}
+	defer destFile.Close()
+
+	if _, err := io.Copy(destFile, sourceFile); err != nil {
+		return fmt.Errorf("could not copy file: %v", err)
+	}
+
+	sourceInfo, err := os.Stat(src)
+	if err != nil {
+		return fmt.Errorf("could not stat source file: %v", err)
+	}
+
+	if err := os.Chmod(dst, sourceInfo.Mode()); err != nil {
+		return fmt.Errorf("could not set file permissions: %v", err)
+	}
+
+	return nil
+}

src/php/finalize/finalize_test.go

@@ -405,7 +405,7 @@ var _ = Describe("Finalize", func() {
 			})
 		})
 
-		Context("when rewrite binary doesn't exist", func() {
+		Context("when rewrite binary doesn't exist in bin/", func() {
 			It("returns an error", func() {
 				finalizer = &finalize.Finalizer{
 					Manifest: manifest,
@@ -463,7 +463,7 @@ var _ = Describe("Finalize", func() {
 			Expect(bpBinDir).To(BeADirectory())
 		})
 
-		It("copies rewrite binary to .bp/bin", func() {
+		It("copies pre-compiled rewrite binary to .bp/bin", func() {
 			stager := &testStager{
 				buildDir: buildDir,
 				depsDir:  depsDir,
@@ -486,7 +486,7 @@ var _ = Describe("Finalize", func() {
 			rewriteSrc := filepath.Join(buildDir, "bin", "rewrite")
 			err = os.MkdirAll(filepath.Dir(rewriteSrc), 0755)
 			Expect(err).To(BeNil())
-			err = os.WriteFile(rewriteSrc, []byte("#!/bin/bash\necho test\n"), 0755)
+			err = os.WriteFile(rewriteSrc, []byte("#!/bin/bash\necho test rewrite\n"), 0755)
 			Expect(err).To(BeNil())
 
 			optionsFile := filepath.Join(buildDir, ".bp-config", "options.json")
@@ -498,13 +498,12 @@ var _ = Describe("Finalize", func() {
 			err = finalizer.CreateStartScript()
 			Expect(err).To(BeNil())
 
-			// Verify rewrite binary was copied
 			rewriteDst := filepath.Join(buildDir, ".bp", "bin", "rewrite")
 			Expect(rewriteDst).To(BeAnExistingFile())
 
 			contents, err := os.ReadFile(rewriteDst)
 			Expect(err).To(BeNil())
-			Expect(string(contents)).To(ContainSubstring("echo test"))
+			Expect(string(contents)).To(ContainSubstring("echo test rewrite"))
 		})
 	})