fixup! cmake: Redefine configuration flags

Reorder `CMAKE_<LANG>_FLAGS` and `CMAKE_<LANG>_FLAGS_<CONFIG>`.

CMakeLists.txt

@@ -288,6 +288,8 @@ else()
   unset(debug_flags)
 endif()
 
+reorder_flags_for_all_configs()
+
 include(cmake/optional_qt.cmake)
 
 include(cmake/optional.cmake)
@@ -412,19 +414,18 @@ else()
   set(cross_status "FALSE")
 endif()
 message("Cross compiling ....................... ${cross_status}")
-message("Preprocessor defined macros ........... ${definitions_ALL}")
 message("C compiler ............................ ${CMAKE_C_COMPILER}")
-message("CFLAGS ................................ ${CMAKE_C_FLAGS}")
 message("C++ compiler .......................... ${CMAKE_CXX_COMPILER}")
-message("CXXFLAGS .............................. ${CMAKE_CXX_FLAGS}")
 include(GetTargetInterface)
+print_config_flags()
+message("Preprocessor defined macros ........... ${definitions_ALL}")
 get_target_interface(common_compile_options core_interface COMPILE_OPTIONS)
 message("Common compile options ................ ${common_compile_options}")
 get_target_interface(common_link_options core_interface LINK_OPTIONS)
 message("Common link options ................... ${common_link_options}")
 message("Linker flags for executables .......... ${CMAKE_EXE_LINKER_FLAGS}")
 message("Linker flags for shared libraries ..... ${CMAKE_SHARED_LINKER_FLAGS}")
-print_config_flags()
+message("")
 message("Use assembly routines ................. ${ASM}")
 message("Attempt to harden executables ......... ${HARDENING}")
 message("Treat compiler warnings as errors ..... ${WERROR}")

cmake/module/ProcessConfigurations.cmake

@@ -54,6 +54,27 @@ function(set_default_config config)
   endif()
 endfunction()
 
+#[=[
+By default, CMake passes flags in the CMAKE_<LANG>_FLAGS variable before
+those in the per-configuration CMAKE_<LANG>_FLAGS_<CONFIG> variable.
+Such a behaviour breaks our integration with the depends build system.
+Therefore, we _append_ flags from the CMAKE_<LANG>_FLAGS variable to
+the CMAKE_<LANG>_FLAGS_<CONFIG> ones explicitly, while clearing the former.
+]=]
+function(reorder_flags_for_all_configs)
+  get_all_configs(all_configs)
+  foreach(config IN LISTS all_configs)
+    string(TOUPPER "${config}" config_uppercase)
+    string(STRIP "${CMAKE_C_FLAGS_${config_uppercase}} ${CMAKE_C_FLAGS}" CMAKE_C_FLAGS_${config_uppercase})
+    set(CMAKE_C_FLAGS_${config_uppercase} "${CMAKE_C_FLAGS_${config_uppercase}}" PARENT_SCOPE)
+    string(STRIP "${CMAKE_CXX_FLAGS_${config_uppercase}} ${CMAKE_CXX_FLAGS}" CMAKE_CXX_FLAGS_${config_uppercase})
+    set(CMAKE_CXX_FLAGS_${config_uppercase} "${CMAKE_CXX_FLAGS_${config_uppercase}}" PARENT_SCOPE)
+    set(CMAKE_OBJCXX_FLAGS_${config_uppercase} "${CMAKE_CXX_FLAGS_${config_uppercase}}" PARENT_SCOPE)
+  endforeach()
+  set(CMAKE_C_FLAGS PARENT_SCOPE)
+  set(CMAKE_CXX_FLAGS PARENT_SCOPE)
+endfunction()
+
 function(remove_c_flag_from_all_configs flag)
   get_all_configs(all_configs)
   foreach(config IN LISTS all_configs)