fix: serialize dist copies via a ninja job pool to avoid copy races

Replaces the per-destination copy-target deduplication with a depth-1
JOB_POOL, restoring the original per-target copy structure while still
preventing concurrent writes to the shared Binaries directory.

Author: FlyAndNotDown

CMake/Target.cmake

@@ -12,6 +12,11 @@ set(AUX_TARGETS_FOLDER "${BASE_TARGETS_FOLDER}/Aux")
 
 get_cmake_property(with_multi_config_generator GENERATOR_IS_MULTI_CONFIG)
 
+# Runtime-dependency and resource copies all land in the shared per-sub-project Binaries directory, and many targets copy
+# an overlapping set of files there. Running those copies concurrently races on the same destination files (intermittent
+# "Error copying file" failures under Ninja), so funnel them through a depth-1 job pool to serialize their execution.
+set_property(GLOBAL PROPERTY JOB_POOLS exp_copy=1)
+
 if (BUILD_TEST)
     enable_testing()
     add_compile_definitions(BUILD_TEST=1)
@@ -86,37 +91,6 @@ function(exp_gather_target_runtime_dependencies_recurse)
     set(${arg_OUT_DEP_TARGET} ${result_dep_target} PARENT_SCOPE)
 endfunction()
 
-function(exp_add_shared_copy_target)
-    set(options "")
-    set(singleValueArgs KEY SRC DST MAKE_DIR OUTPUT_TARGET)
-    set(multiValueArgs DEPENDS)
-    cmake_parse_arguments(arg "${options}" "${singleValueArgs}" "${multiValueArgs}" ${ARGN})
-
-    string(MAKE_C_IDENTIFIER "${arg_KEY}" key_id)
-    set(registry_property EXP_SHARED_COPY_TARGET_${SUB_PROJECT_NAME}_${key_id})
-
-    get_property(copy_target GLOBAL PROPERTY ${registry_property})
-    if (NOT copy_target)
-        set(copy_target ${SUB_PROJECT_NAME}.Copy.${key_id})
-        if (DEFINED arg_MAKE_DIR)
-            set(copy_commands COMMAND ${CMAKE_COMMAND} -E make_directory ${arg_MAKE_DIR})
-        else ()
-            set(copy_commands "")
-        endif ()
-        list(APPEND copy_commands COMMAND ${CMAKE_COMMAND} -E copy_if_different ${arg_SRC} ${arg_DST})
-
-        add_custom_target(${copy_target} ${copy_commands})
-        set_target_properties(${copy_target} PROPERTIES FOLDER ${AUX_TARGETS_FOLDER})
-        set_property(GLOBAL PROPERTY ${registry_property} ${copy_target})
-    endif ()
-
-    if (arg_DEPENDS)
-        add_dependencies(${copy_target} ${arg_DEPENDS})
-    endif ()
-
-    set(${arg_OUTPUT_TARGET} ${copy_target} PARENT_SCOPE)
-endfunction()
-
 function(exp_process_runtime_dependencies)
     set(options NOT_INSTALL)
     set(singleValueArgs NAME)
@@ -136,37 +110,29 @@ function(exp_process_runtime_dependencies)
             OUT_DEP_TARGET dep_dep_targets
         )
         list(APPEND runtime_deps ${dep_target_runtime_deps})
+        list(APPEND dep_targets ${dep_dep_targets})
     endforeach ()
 
-    if (runtime_deps)
-        list(REMOVE_DUPLICATES runtime_deps)
-    endif ()
-
-    exp_get_runtime_output_dir(OUTPUT out_dir)
-    foreach (r ${runtime_deps})
-        set(copy_depends "")
-        if ("${r}" MATCHES "^\\$<TARGET_FILE:(.+)>$")
-            set(producer ${CMAKE_MATCH_1})
-            if (TARGET ${producer})
-                get_target_property(producer_imported ${producer} IMPORTED)
-                if (NOT producer_imported)
-                    set(copy_depends ${producer})
-                endif ()
-            endif ()
-        endif ()
-
-        exp_add_shared_copy_target(
-            KEY ${r}
-            SRC ${r}
-            DST ${out_dir}
-            MAKE_DIR ${out_dir}
-            DEPENDS ${copy_depends}
-            OUTPUT_TARGET copy_target
+    set(copy_commands COMMAND ${CMAKE_COMMAND} -E make_directory $<TARGET_FILE_DIR:${arg_NAME}>)
+    foreach(r ${runtime_deps})
+        list(APPEND copy_commands COMMAND ${CMAKE_COMMAND} -E copy_if_different ${r} $<TARGET_FILE_DIR:${arg_NAME}>)
+    endforeach()
+    if (NOT "${copy_commands}" STREQUAL "")
+        set(custom_target_name ${arg_NAME}.CopyRuntimeDeps)
+        add_custom_target(
+            ${custom_target_name}
+            ${copy_commands}
+            JOB_POOL exp_copy
         )
-        add_dependencies(${arg_NAME} ${copy_target})
-    endforeach ()
 
-    if (NOT arg_NOT_INSTALL AND runtime_deps)
+        add_dependencies(${arg_NAME} ${custom_target_name})
+        foreach (t ${dep_targets})
+            add_dependencies(${custom_target_name} ${t})
+        endforeach ()
+
+        set_target_properties(${custom_target_name} PROPERTIES FOLDER ${AUX_TARGETS_FOLDER})
+    endif ()
+    if (NOT arg_NOT_INSTALL AND NOT "${runtime_deps}" STREQUAL "")
         install(
             FILES ${runtime_deps} DESTINATION ${SUB_PROJECT_NAME}/Binaries
         )
@@ -193,28 +159,30 @@ function(exp_add_resources_copy_command)
     set(multiValueArgs RES)
     cmake_parse_arguments(arg "${options}" "${singleValueArgs}" "${multiValueArgs}" ${ARGN})
 
-    exp_get_runtime_output_dir(OUTPUT out_dir)
     foreach(r ${arg_RES})
         exp_expand_resource_path_expression(
             INPUT ${r}
             OUTPUT_SRC src
             OUTPUT_DST dst
         )
 
-        exp_add_shared_copy_target(
-            KEY ${dst}
-            SRC ${src}
-            DST ${out_dir}/${dst}
-            OUTPUT_TARGET copy_target
-        )
-        add_dependencies(${arg_NAME} ${copy_target})
+        list(APPEND copy_commands COMMAND ${CMAKE_COMMAND} -E copy_if_different ${src} $<TARGET_FILE_DIR:${arg_NAME}>/${dst})
 
         cmake_path(SET dst_path NORMALIZE "${SUB_PROJECT_NAME}/Binaries/${dst}")
         cmake_path(GET dst_path PARENT_PATH dst_dir)
         if (NOT arg_NOT_INSTALL)
             install(FILES ${src} DESTINATION ${dst_dir})
         endif ()
     endforeach()
+
+    set(copy_res_target_name ${arg_NAME}.CopyRes)
+    add_custom_target(
+        ${copy_res_target_name}
+        ${copy_commands}
+        JOB_POOL exp_copy
+    )
+    set_target_properties(${copy_res_target_name} PROPERTIES FOLDER ${AUX_TARGETS_FOLDER})
+    add_dependencies(${arg_NAME} ${copy_res_target_name})
 endfunction()
 
 function(exp_gather_target_libs)