Use CMake built-in dir create function instead of hard-coded mkdir (#…

…108)

... Because all systems may not play nice with `mkdir -p`.

src/substrait/proto/CMakeLists.txt

@@ -30,9 +30,9 @@ foreach(PROTO_FILE IN LISTS PROTOBUF_FILELIST)
       ${GENERATED_PROTO_MIDLEVEL_DIR}/${RELATIVE_PROTO_PATH})
 
   cmake_path(GET GENERATED_PROTO_FILE PARENT_PATH GENERATED_PROTO_DIR)
+  file(MAKE_DIRECTORY ${GENERATED_PROTO_DIR})
   add_custom_command(
     OUTPUT ${GENERATED_PROTO_FILE}
-    COMMAND mkdir -p ${GENERATED_PROTO_DIR}
     COMMAND ${PERL_EXECUTABLE} ${UPDATE_PROTO_PACKAGE_TOOL} ${PROTO_FILE} >
             ${GENERATED_PROTO_FILE}
     DEPENDS ${PROTO_FILE} ${UPDATE_PROTO_PACKAGE_TOOL}