Sema: Stop adding Windows implib link inputs for extern "..." syntax.

[alexrp]

Closes #23971.

Release Notes

When encountering a declaration such as

pub extern "ws2_32" fn closesocket(s: SOCKET) callconv(.winapi) i32;

the Zig compiler will no longer automatically add the import library for ws2_32.dll as a link input. Users will now need to manually link ws2_32 either by passing -lws2_32 on the command line, or by calling b.linkSystemLibrary("ws2_32") in a build script (conditioned on target.os.tag == .windows).

This change was made because the old behavior obscured which DLLs a Windows binary actually depends on. Zig favors explicitness, and users are required to specify link dependencies explicitly for all other targets, making the old Windows behavior inconsistent. Finally, semantic analysis of Zig code having the ability to introduce new link inputs in the compilation pipeline imposed undesirable constraints on the compiler implementation.

Notably, there are two exceptions to this change: ntdll.dll and kernel32.dll. As these DLLs are always loaded into Windows processes anyway, they are also implicitly linked by the compiler. These exceptions should mitigate the ecosystem breakage somewhat.

[alexrp]

💣