Avoid modifying CMAKE_DEBUG_POSTFIX globally in subprojects

[Copilot]

Setting CMAKE_DEBUG_POSTFIX via CACHE STRING in Lcms2Options.cmake pollutes the global CMake cache, silently overriding a parent project's postfix configuration when Little-CMS is consumed via add_subdirectory.

Changes

• cmake/Lcms2Options.cmake — Remove the global CMAKE_DEBUG_POSTFIX cache entry entirely
• cmake/Lcms2Library.cmake — Set DEBUG_POSTFIX "d" directly on each library target via _lcms2_apply_common_settings()
• cmake/Lcms2Tools.cmake — Set DEBUG_POSTFIX "d" on each tool target in _lcms2_add_tool()
• cmake/Lcms2Tests.cmake — Set DEBUG_POSTFIX "d" on the testcms target

Instead of relying on CMAKE_DEBUG_POSTFIX propagating to new targets at creation time, the postfix is now applied explicitly per-target:

# Before — contaminates global/cache scope
if(MSVC AND NOT DEFINED CMAKE_DEBUG_POSTFIX)
  set(CMAKE_DEBUG_POSTFIX "d" CACHE STRING "Debug postfix for binaries and libraries")
endif()

# After — scoped to this project's targets only
if(MSVC)
  set_target_properties(${tgt} PROPERTIES DEBUG_POSTFIX "d")
endif()

This preserves identical MSVC output naming behavior while having zero effect on any parent project's CMake state.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Avoid modifying CMAKE_DEBUG_POSTFIX globally in subprojects</issue_title>
<issue_description>The current code sets a default debug postfix as follows:

cmake/Lcms2Options.cmake

Default debug postfix for MSVC builds.

if(MSVC AND NOT DEFINED CMAKE_DEBUG_POSTFIX)
set(CMAKE_DEBUG_POSTFIX "d" CACHE STRING "Debug postfix for binaries and libraries")
endif()

However, modifying CMAKE_DEBUG_POSTFIX in this way affects the global CMake state. When this project is included via add_subdirectory, it unintentionally overrides the parent project's configuration.

This can lead to unexpected behavior in larger builds where different subprojects may rely on different postfix settings.</issue_description>

<agent_instructions>CMake scripts are still a test in progress, make a deep check that everything is ok. Don't change anything out of CMake scope</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Avoid modifying CMAKE_DEBUG_POSTFIX globally in subprojects #547

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