Improvements to Protobuf.Makefile (#356)

Improvements to `Protobuf.Makefile`. Also see
https://github.com/apple/container/pull/821.

Protobuf.Makefile

@@ -1,12 +1,26 @@
+# Copyright © 2025 Apple Inc. and the Containerization project authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 LOCAL_DIR := $(ROOT_DIR)/.local
-LOCALBIN := $(LOCAL_DIR)/bin
+LOCAL_BIN_DIR := $(LOCAL_DIR)/bin
 
-## Versions
-PROTOC_VERSION=26.1
+# Versions
+PROTOC_VERSION := 26.1
 
-# protoc binary installation
-PROTOC_ZIP = protoc-$(PROTOC_VERSION)-osx-universal_binary.zip
-PROTOC = $(LOCALBIN)/protoc@$(PROTOC_VERSION)/protoc
+# Protoc binary installation
+PROTOC_ZIP := protoc-$(PROTOC_VERSION)-osx-universal_binary.zip
+PROTOC := $(LOCAL_BIN_DIR)/protoc@$(PROTOC_VERSION)/protoc
 $(PROTOC):
 	@echo Downloading protocol buffers...
 	@mkdir -p $(LOCAL_DIR)
@@ -16,14 +30,13 @@ $(PROTOC):
 	@unzip -o $(PROTOC_ZIP) 'include/*' -d $(dir $@)
 	@rm -f $(PROTOC_ZIP)
 
-protoc_gen_grpc_swift:
-	swift build --product protoc-gen-grpc-swift
-
+.PHONY: protoc-gen-swift
 protoc-gen-swift:
-	swift build --product protoc-gen-swift
+	@$(SWIFT) build --product protoc-gen-swift
+	@$(SWIFT) build --product protoc-gen-grpc-swift
 
 .PHONY: protos
-protos: $(PROTOC) protoc_gen_grpc_swift protoc-gen-swift
+protos: $(PROTOC) protoc-gen-swift
 	@echo Generating protocol buffers source code...
 	@$(PROTOC) Sources/Containerization/SandboxContext/SandboxContext.proto \
 		--plugin=protoc-gen-grpc-swift=$(BUILD_BIN_DIR)/protoc-gen-grpc-swift \
@@ -35,3 +48,8 @@ protos: $(PROTOC) protoc_gen_grpc_swift protoc-gen-swift
 		--swift_opt=Visibility=Public \
 		-I.
 	@"$(MAKE)" update-licenses
+
+.PHONY: clean-proto-tools
+clean-proto-tools:
+	@echo Cleaning proto tools...
+	@rm -rf $(LOCAL_DIR)/bin/protoc*

licenserc.toml

@@ -4,6 +4,7 @@ headerPath = "scripts/license-header.txt"
 
 includes = [
     "Makefile",
+    "*.Makefile",
     "*.swift",
     "*.h",
     "*.cpp",