added handling and tests for when user doesn't add rpms

pkg/build/rpm.go

@@ -29,6 +29,15 @@ func (b *Builder) getRPMFileNames(rpmSourceDir string) ([]string, error) {
 
 func (b *Builder) copyRPMs() error {
 	rpmSourceDir := filepath.Join(b.buildConfig.ImageConfigDir, "rpms")
+	// Only proceed with copying the RPMs if the directory exists
+	_, err := os.Stat(rpmSourceDir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		} else {
+			return fmt.Errorf("checking for rpm directory at %s: %w", rpmSourceDir, err)
+		}
+	}
 	rpmDestDir := b.combustionDir
 
 	rpmFileNames, err := b.getRPMFileNames(rpmSourceDir)

pkg/build/rpm_test.go

@@ -106,3 +106,20 @@ func TestGetRPMFileNamesNoRPMs(t *testing.T) {
 
 	assert.Empty(t, rpmFileNames)
 }
+
+func TestCopyRPMsNoRPMDir(t *testing.T) {
+	// Setup
+	bc := config.BuildConfig{
+		ImageConfigDir: "../config/ThisDirDoesNotExist",
+	}
+	builder := New(nil, &bc)
+	err := builder.prepareBuildDir()
+	require.NoError(t, err)
+	defer os.Remove(builder.eibBuildDir)
+
+	// Test
+	err = builder.copyRPMs()
+
+	// Verify
+	require.NoError(t, err)
+}