[DRAFT] Support build proto as shared lib on Windows

[owent]

Fixes #3665

Changes

• Set dllexport_decl for proto targets and can be built as shared on windows.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[Copilot]

Pull Request Overview

This PR enables building Protocol Buffer (protobuf) targets as shared libraries on Windows by implementing proper DLL export/import declarations. Previously, protobuf targets were forced to be static libraries on Windows, but this change adds the necessary infrastructure to support shared library builds across platforms.

Key changes:

• Added CMake helper functions for managing export/import declarations across different compilers and platforms
• Modified protobuf generation to include dllexport_decl parameter for proper Windows DLL support
• Removed Windows-specific restriction forcing static library builds for protobuf targets

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
cmake/tools.cmake	Adds utility functions for generating platform and compiler-specific DLL export/import declarations
cmake/opentelemetry-proto.cmake	Integrates DLL declarations into protobuf targets, removes Windows static-only restriction, and adds formatting improvements

[Copilot]

The use of WINDOWS_EXPORT_ALL_SYMBOLS for the gRPC target differs from the explicit export declaration approach used for the base proto target. This inconsistency may cause confusion. Consider documenting why gRPC requires automatic symbol export while the base target uses manual declarations via OPENTELEMETRY_PROTO_API.

[Copilot]

The SunPro compiler check uses an undefined variable SunPro instead of checking CMAKE_CXX_COMPILER_ID. This condition will never be true. Change to elseif(CMAKE_CXX_COMPILER_ID STREQUAL \"SunPro\") to properly detect the SunPro compiler.

[Copilot]

The SunPro compiler check uses an undefined variable SunPro instead of checking CMAKE_CXX_COMPILER_ID. This condition will never be true. Change to elseif(CMAKE_CXX_COMPILER_ID STREQUAL \"SunPro\") to properly detect the SunPro compiler.

Suggested change

	elseif(SunPro)
	elseif(CMAKE_CXX_COMPILER_ID STREQUAL "SunPro")

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.95%. Comparing base (70daba9) to head (c45538c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3714      +/-   ##
==========================================
+ Coverage   89.90%   89.95%   +0.06%     
==========================================
  Files         225      225              
  Lines        7281     7103     -178     
==========================================
- Hits         6545     6389     -156     
+ Misses        736      714      -22     

see 48 files with indirect coverage changes

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