CMake config: Set minimum C++ version needed in a different way

This setting should be overwritten if CMake find that some library needs
an even more modern version.

.github/workflows/c.yml

@@ -68,7 +68,7 @@ jobs:
     env:
       CC: clang
       CXX: clang++
-      CXXFLAGS: -Werror -Wall -pedantic -std=c++17
+      CXXFLAGS: -Werror -Wall -pedantic
       BUILD_TYPE: Debug
     steps:
       - uses: actions/checkout@v4

CMakeLists.txt

@@ -4,6 +4,14 @@ project(osmpbf VERSION 1.5.0)
 
 include(GNUInstallDirs)
 
+# This is needed for the protobuf_generate_cpp() function to work on newer
+# versions of the Protobuf CMake config.
+set(protobuf_MODULE_COMPATIBLE ON CACHE BOOL "")
+
+# This is needed so that we pick up the (more modern) CONFIG mode cmake file
+# before the (older) MODULE mode cmake config file. Seems to be needed on macOS.
+set(CMAKE_FIND_PACKAGE_PREFER_CONFIG TRUE)
+
 find_package(Protobuf REQUIRED)
 
 add_subdirectory(osmpbf)

osmpbf/CMakeLists.txt

@@ -1,12 +1,13 @@
 protobuf_generate_cpp(CPPS HS fileformat.proto osmformat.proto)
 
 add_library(osmpbf STATIC ${CPPS})
+target_compile_features(osmpbf PUBLIC cxx_std_11)
+target_link_libraries(osmpbf PRIVATE protobuf::libprotobuf)
 target_include_directories(osmpbf SYSTEM PUBLIC ${Protobuf_INCLUDE_DIRS})
-set_property(TARGET osmpbf PROPERTY CXX_STANDARD 11)
 install(TARGETS osmpbf ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
 
 add_library(osmpbf_shared SHARED ${CPPS})
-set_property(TARGET osmpbf_shared PROPERTY CXX_STANDARD 11)
+target_compile_features(osmpbf_shared PUBLIC cxx_std_11)
 target_link_libraries(osmpbf_shared PRIVATE protobuf::libprotobuf)
 target_include_directories(osmpbf_shared SYSTEM PUBLIC ${Protobuf_INCLUDE_DIRS})
 set_target_properties(osmpbf_shared PROPERTIES OUTPUT_NAME osmpbf