data_to_c: CMake: Speed-up data_to_c

This moves the logic to create the parent folder to data_to_c itself
rather than having cmake do it, preventing several thousand cmake instances
to be started.

see pr#141404 for details/benchmarks

Pull Request: https://projects.blender.org/blender/blender/pulls/141404

build_files/cmake/macros.cmake

@@ -999,7 +999,6 @@ function(data_to_c
 
   add_custom_command(
     OUTPUT ${file_to}
-    COMMAND ${CMAKE_COMMAND} -E make_directory ${_file_to_path}
     COMMAND "$<TARGET_FILE:datatoc>" ${file_from} ${file_to}
     DEPENDS ${file_from} datatoc)
 
@@ -1026,7 +1025,6 @@ function(data_to_c_simple
 
   add_custom_command(
     OUTPUT  ${_file_to}
-    COMMAND ${CMAKE_COMMAND} -E make_directory ${_file_to_path}
     COMMAND "$<TARGET_FILE:datatoc>" ${_file_from} ${_file_to}
     DEPENDS ${_file_from} datatoc)
 
@@ -1055,7 +1053,6 @@ function(glsl_to_c
 
   add_custom_command(
     OUTPUT  ${_file_to} ${_file_meta}
-    COMMAND ${CMAKE_COMMAND} -E make_directory ${_file_to_path}
     COMMAND "$<TARGET_FILE:glsl_preprocess>" ${_file_from} ${_file_tmp} ${_file_meta}
     COMMAND "$<TARGET_FILE:datatoc>" ${_file_tmp} ${_file_to}
     DEPENDS ${_file_from} datatoc glsl_preprocess)

source/blender/datatoc/datatoc.cc

@@ -10,6 +10,8 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
+#include <filesystem>
+#include <iostream>
 
 // #define VERBOSE
 
@@ -63,6 +65,19 @@ int main(int argc, char **argv)
   printf("Making C file <%s>\n", argv[2]);
 #endif
 
+  /* We make the required directories here rather than having the build system
+   * do the work for us, as having cmake do it leads to several thousand cmake
+   * instances being launched, leading to significant overhead, see pr #141404
+   * for details. */
+  std::filesystem::path parent_dir = std::filesystem::path(argv[2]).parent_path();
+  std::error_code ec;
+  if (!std::filesystem::create_directories(parent_dir, ec)) {
+    if (ec) {
+      std::cerr << "Unable to create " << parent_dir << " : " << ec.message() << std::endl;
+      exit(1);
+    }
+  }
+
   argv_len = int(strlen(argv[1]));
   for (i = 0; i < argv_len; i++) {
     if (argv[1][i] == '.') {