Fix generated proto exports in Windows shared builds

[PharahAmari]

Problem

When generated proto object libraries are compiled as part of a shared MSVC build, OR_TOOLS_COMPILE_DEFINITIONS can provide the consumer-side dllimport definition while the target also adds its private dllexport definition. Both definitions then appear on the compiler command line. If dllimport wins by command-line ordering, MSVC rejects definitions of generated static data members with C2491.

Change

Filter the current generated proto target's consumer-side import macro out of the common compile definitions before applying the target's explicit interface/private import/export definitions.

Non-MSVC and static builds are unchanged.

Validation

• Configured and built a native Windows shared OR-Tools Python wheel with MSVC.
• Verified generated proto compilation contains only the target's dllexport definition.
• Successfully linked ortools.dll and all Python extension modules.
• Imported MathOpt protobuf modules and solved a CP-SAT smoke model from the resulting wheel.

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[Mizux]

why not removing theses lines (53 to 55) from cpp.cmake instead of filter out later ?

or-tools/cmake/cpp.cmake

Lines 53 to 55 in 5d0f4ac

	list(APPEND OR_TOOLS_COMPILE_DEFINITIONS "OR_ORTOOLS_PROTO_DLL=__declspec(dllimport)")
	else()
	list(APPEND OR_TOOLS_COMPILE_DEFINITIONS "OR_ORTOOLS_PROTO_DLL=")

knowing we already have:

or-tools/cmake/cpp.cmake

Lines 567 to 572 in 5d0f4ac

	if(MSVC AND BUILD_SHARED_LIBS)
	target_compile_definitions(${PROTO_NAME}_proto INTERFACE "OR_${PROTO_UPPER_NAME}_PROTO_DLL=__declspec(dllimport)")
	target_compile_definitions(${PROTO_NAME}_proto PRIVATE "OR_${PROTO_UPPER_NAME}_PROTO_DLL=__declspec(dllexport)")
	else()
	target_compile_definitions(${PROTO_NAME}_proto PUBLIC "OR_${PROTO_UPPER_NAME}_PROTO_DLL=")
	endif()

and

or-tools/cmake/cpp.cmake

Lines 602 to 604 in 5d0f4ac

	generate_proto_library(
	NAME ortools
	FILES ${OR_TOOLS_PROTO_FILES})