cmake: fix recent protobuf build with cmake

The CMake module is used by default but isn't compatible with
recent protobuf version.

Try to first look for a protobuf config then fallback to legacy
cmake module.
Signed-off-by: Clément Péron <peron.clem@gmail.com>

build-cmake/CMakeLists.txt

@@ -15,7 +15,11 @@ if (MSVC AND NOT BUILD_SHARED_LIBS)
 	SET(Protobuf_USE_STATIC_LIBS ON)
 endif (MSVC AND NOT BUILD_SHARED_LIBS)
 
-FIND_PACKAGE(Protobuf REQUIRED)
+FIND_PACKAGE(Protobuf CONFIG)
+if(NOT Protobuf_FOUND)
+  MESSAGE(STATUS "Protobuf CMake config not found fallback to Cmake Module")
+  FIND_PACKAGE(Protobuf REQUIRED)
+endif()
 file(REAL_PATH "${PROTOBUF_INCLUDE_DIR}" PROTOBUF_INCLUDE_DIR)
 INCLUDE_DIRECTORIES(${PROTOBUF_INCLUDE_DIR})
 
@@ -112,7 +116,7 @@ if (MSVC AND NOT BUILD_SHARED_LIBS)
 	foreach(flag_var
 		CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
 		CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO
-		CMAKE_C_FLAGS CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_RELEASE 
+		CMAKE_C_FLAGS CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_RELEASE
 		CMAKE_C_FLAGS_MINSIZEREL CMAKE_FLAGS_RELWITHDEBINFO)
 	  if(${flag_var} MATCHES "/MD")
 		string(REGEX REPLACE "/MD" "/MT" ${flag_var} "${${flag_var}}")
@@ -316,12 +320,12 @@ ADD_TEST(test-version test-version)
 
 if(WIN32)
     set_tests_properties(
-        test-generated-code 
-        test-generated-code2 
-        test-generated-code3 
-        test-issue220 
-        test-issue251 
-        test-version 
+        test-generated-code
+        test-generated-code2
+        test-generated-code3
+        test-issue220
+        test-issue251
+        test-version
         PROPERTIES ENVIRONMENT "PATH=${WINDOWS_PATH_VARIABLE}\\;$<TARGET_FILE_DIR:protoc-gen-c>" )
 endif(WIN32)