Fix build issues in C and add CMake support.

[GyuH13]

This PR fixes a build issue in the C SDK and introduces CMake support.

• related emanual PR: Support cmake build in c and cpp emanual#1852

Changes

1. Fix Windows Build Issue

In port_handler.h, the following variables were declared as extern:

• int g_used_port_num
• uint8_t *g_is_using

However, these variables were only defined under the Linux implementation in port_handler.c, which caused build failures on Windows.
This PR adds the missing definitions for Windows to resolve the issue.

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2. Introduce CMake Support

CMake support has been added to unify the build system.

• Previously, the build system was separated by operating system and architecture (bit).
• This has now been consolidated into a single CMake-based build system.
• The installed SDK can now be used via find_package() in CMake.

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3. Deprecation Plan for Legacy Make System

The existing Make-based build system will be kept temporarily for compatibility.

• It will remain during a transition period.
• It is planned to be removed after approximately 3 months.

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4. Installation Path Changes (C vs C++)

Previously, when installing the C SDK via the Make system, files were installed under:

/usr/local/include/dynamixel_sdk/*

Since this path is shared between C and C++ SDKs, it can cause ambiguity.

To address this:

• The CMake build for the C SDK now uses a distinct prefix and project name:

  • dynamixel_sdk_c

This ensures clear separation between C and C++ installations and avoids conflicts.

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Summary

• Fixed Windows build issue due to missing global variable definitions
• Added unified CMake build support
• Enabled usage via find_package()
• Introduced a clear separation between C and C++ SDK installations
• Planned deprecation of legacy Make build system

Thank you.

[gemini-code-assist]

Code Review

This pull request updates the Dynamixel SDK to version 4.0.4 and introduces a unified CMake build system for the C and C++ libraries, including installation and uninstallation scripts. Feedback identifies a regex error in the C SDK's uninstallation logic and suggests refining the C++ SDK's exported include directories to simplify consumer header inclusion. Additionally, a refactor is recommended for port_handler.c to consolidate global variable definitions and reduce platform-specific code duplication.

[nhw-robotis]

GOOD

[sunghowoo]

LGTM