Please pay attention to the following error taken from the question:

In file included from /home/rentaro/dyna_ws/src/my_dyna_pkgs/dynamixel-workbench/dynamixel_workbench_toolbox/src/dynamixel_workbench_toolbox/dynamixel_driver.cpp:19:
/home/rentaro/dyna_ws/src/my_dyna_pkgs/dynamixel-workbench/dynamixel_workbench_toolbox/src/dynamixel_workbench_toolbox/../../include/dynamixel_workbench_toolbox/dynamixel_driver.h:29:12: fatal error: dynamixel_sdk/dynamixel_sdk.h: No such file or directory
   29 |   #include "dynamixel_sdk/dynamixel_sdk.h"
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

It can not find dynamixel_sdk. Therefore, you need to install it. There are various ways to install it. Since the question is for ROS Noetic, please remember to adapt commands to your ROS distro. Let's discuss them below:

Install from Source

1. Get the source code of DynamixelSDK.

   ravi@dell:~$ mkdir dynamixel
   ravi@dell:~$ cd dynamixel/
   ravi@dell:~/dynamixel$ git clone --branch noetic-devel https://github.com/ROBOTIS-GIT/DynamixelSDK.git
   Cloning into 'DynamixelSDK'...
   remote: Enumerating objects: 13727, done.
   remote: Counting objects: 100% (1101/1101), done.
   remote: Compressing objects: 100% (486/486), done.
   remote: Total 13727 (delta 539), reused 1047 (delta 524), pack-reused 12626
   Receiving objects: 100% (13727/13727), 28.50 MiB | 5.84 MiB/s, done.
   Resolving deltas: 100% (7787/7787), done.
   

2. Compile the source code. Here I am compiling 64 bit version.

   ravi@dell:~/dynamixel$ cd DynamixelSDK/c++/build/linux64
   ravi@dell:~/dynamixel/DynamixelSDK/c++/build/linux64$ make
   mkdir -p ./.objects/
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/group_bulk_read.cpp -o .objects/group_bulk_read.o
   ../../src/dynamixel_sdk/group_bulk_read.cpp: In member function ‘bool dynamixel::GroupBulkRead::getError(uint8_t, uint8_t*)’:
   ../../src/dynamixel_sdk/group_bulk_read.cpp:235:19: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
     235 |   return error[0] = error_list_[id][0];
         |          ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/group_bulk_write.cpp -o .objects/group_bulk_write.o
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/group_sync_read.cpp -o .objects/group_sync_read.o
   ../../src/dynamixel_sdk/group_sync_read.cpp: In member function ‘bool dynamixel::GroupSyncRead::getError(uint8_t, uint8_t*)’:
   ../../src/dynamixel_sdk/group_sync_read.cpp:204:19: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
     204 |   return error[0] = error_list_[id][0];
         |          ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/group_sync_write.cpp -o .objects/group_sync_write.o
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/packet_handler.cpp -o .objects/packet_handler.o
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/port_handler.cpp -o .objects/port_handler.o
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/protocol1_packet_handler.cpp -o .objects/protocol1_packet_handler.o
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/protocol2_packet_handler.cpp -o .objects/protocol2_packet_handler.o
   g++ -O2 -O3 -DLINUX -D_GNU_SOURCE -Wall -c -I../../include/dynamixel_sdk -m64 -fPIC -g -c ../../src/dynamixel_sdk/port_handler_linux.cpp -o .objects/port_handler_linux.o
   g++ -shared -fPIC -m64 -o ./libdxl_x64_cpp.so ./.objects/group_bulk_read.o ./.objects/group_bulk_write.o ./.objects/group_sync_read.o ./.objects/group_sync_write.o ./.objects ...