build: Workaround FindProtobuf lacking support for Protobuf >= 22

1. If we can find a Protobuf with a CMake pkg, we are good.
2. Otherwise fall back to FindProtobuf.
3. If we find Protobuf >= 22 and do not detect the missing `absl::`
   target (this is a guess that `absl::` targets will exist once
   FindProtobuf supports Protobuf >= 22), we set Protobuf as NOTFOUND.

Side notes:
Old CMake versions (< 3.27) see Protobuf >= 21 as major version 4.21+.

See also:
* https://github.com/protocolbuffers/protobuf/releases/tag/v22.0
* https://protobuf.dev/news/2022-05-06/#versioning
* protocolbuffers/protobuf#12292
* https://gitlab.kitware.com/cmake/cmake/-/issues/24847

(cherry picked from commit 0c09823)

CMakeLists.txt

@@ -173,7 +173,21 @@ endforeach()
 
 find_package2(PUBLIC Pythia6)
 find_package2(PUBLIC Pythia8)
-find_package2(PUBLIC Protobuf)
+# Protobuf https://github.com/protocolbuffers/protobuf/releases/tag/v22.0
+# added a new dependency to abseil which is not handled yet by CMake's
+# FindProtobuf.cmake.
+# https://github.com/protocolbuffers/protobuf/issues/12292 - Let's try to
+# find a Protobuf CMake pkg first and fall back to find module if not found.
+find_package2(PUBLIC Protobuf CONFIG)
+if(NOT Protobuf_FOUND)
+  unset(Protobuf_FOUND CACHE)
+  find_package2(PUBLIC Protobuf)
+  if(    Protobuf_FOUND
+     AND Protobuf_VERSION VERSION_GREATER_EQUAL 4.22
+     AND NOT TARGET absl::raw_logging_internal)
+    set(Protobuf_FOUND NOTFOUND CACHE FORCE)
+  endif()
+endif()
 find_package2(PUBLIC msgpack)
 find_package2(PUBLIC Flatbuffers)
 

examples/advanced/Tutorial3/CMakeLists.txt

@@ -35,23 +35,20 @@ set(sources
   timeBasedSimulation/FairTestDetectorTimeDigiTask.cxx
   timeBasedSimulation/FairTestDetectorTimeRecoTask.cxx
 
-  $<$<BOOL:${Protobuf_FOUND}>:${CMAKE_CURRENT_BINARY_DIR}/FairTestDetectorPayload.pb.cc>
+  $<$<TARGET_EXISTS:protobuf::libprotobuf>:${CMAKE_CURRENT_BINARY_DIR}/FairTestDetectorPayload.pb.cc>
   $<$<BOOL:${Flatbuffers_FOUND}>:${CMAKE_CURRENT_BINARY_DIR}/FairTestDetectorPayloadDigi_generated.h>
   $<$<BOOL:${Flatbuffers_FOUND}>:${CMAKE_CURRENT_BINARY_DIR}/FairTestDetectorPayloadHit_generated.h>
 )
 
 fair_change_extensions_if_exists(.cxx .h FILES "${sources}" OUTVAR headers)
 
-if(Protobuf_FOUND)
-  set(PROTOBUF_USED true)
+if(TARGET protobuf::libprotobuf)
   list(APPEND defs PROTOBUF)
   add_custom_command(
     OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/FairTestDetectorPayload.pb.h ${CMAKE_CURRENT_BINARY_DIR}/FairTestDetectorPayload.pb.cc
-    COMMAND ${PROTOBUF_PROTOC_EXECUTABLE} -I=. --cpp_out=${CMAKE_CURRENT_BINARY_DIR} FairTestDetectorPayload.proto
+    COMMAND $<TARGET_FILE:protobuf::protoc> -I=. --cpp_out=${CMAKE_CURRENT_BINARY_DIR} FairTestDetectorPayload.proto
     WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/MQ/data
   )
-else()
-  set(PROTOBUF_USED false)
 endif()
 
 if(Flatbuffers_FOUND)
@@ -129,7 +126,7 @@ target_link_libraries(${target} PUBLIC
   FairRoot::FairMQ
 
   Boost::serialization
-  $<$<BOOL:${Protobuf_FOUND}>:protobuf::libprotobuf>
+  $<$<TARGET_EXISTS:protobuf::libprotobuf>:protobuf::libprotobuf>
   $<$<BOOL:${Flatbuffers_FOUND}>:${flatbuffers_lib}>
   $<$<BOOL:${msgpack_FOUND}>:msgpackc>