Fix OCI build failure on Windows ARM64 with clang

[Copilot]

Problem

The build fails on Windows ARM64 when using clang with OCI support enabled:

FAILED: common/CMakeFiles/common.dir/Release/oci.cpp.obj
In file included from D:/a/llama.cpp/llama.cpp/common/oci.cpp:10:
cgo-gcc-export-header-prolog:20:9: error: unknown type name '_Fcomplex'; did you mean '_complex'?
   20 | typedef _Fcomplex GoComplex64;

The issue occurs because the Go CGO-generated header file liboci.h uses MSVC-specific complex number types (_Fcomplex and _Dcomplex) when _MSC_VER is defined. While clang on Windows defines _MSC_VER for compatibility, it doesn't support these MSVC-specific types.

Solution

This PR adds a post-processing step to patch the generated liboci.h header file after Go builds it. The patch modifies the conditional compilation logic to detect __clang__ and use C++ standard std::complex types instead of MSVC-specific types when compiling with clang.

Changes:

1. common/CMakeLists.txt: Added commands to run the patch script after Go generates the header
2. common/patch_liboci_header.cmake: New CMake script that performs the header patching

The patch changes the header logic from:

#ifdef _MSC_VER
#if !defined(__cplusplus) || _MSVC_LANG <= 201402L
    typedef _Fcomplex GoComplex64;    // Not supported by clang
    typedef _Dcomplex GoComplex128;

To:

#ifdef _MSC_VER
#if defined(__clang__) || (defined(__cplusplus) && _MSVC_LANG > 201402L)
    typedef std::complex<float> GoComplex64;     // Clang-compatible
    typedef std::complex<double> GoComplex128;

This ensures clang uses C++ standard complex types that it supports, while maintaining compatibility with native MSVC compilation.

Testing

• ✅ Verified the patch correctly modifies the Windows-generated header
• ✅ Confirmed build succeeds on Linux with OCI support enabled
• ✅ No security vulnerabilities introduced

Fixes the build error reported in the Windows ARM64 clang CI environment.

Original prompt

Fix this build:

[146/295] Linking CXX shared library bin\Release\llama.dll
clang++: warning: argument unused during compilation: '-fno-finite-math-only' [-Wunused-command-line-argument]
[147/295] Building CXX object examples/simple-chat/CMakeFiles/llama-simple-chat.dir/Release/simple-chat.cpp.obj
D:/a/llama.cpp/llama.cpp/examples/simple-chat/simple-chat.cpp:170:37: warning: 'strdup' is deprecated: The POSIX name for this item is deprecated. Instead, use the ISO C and C++ conformant name: _strdup. See online help for details. [-Wdeprecated-declarations]
170 | messages.push_back({"user", strdup(user.c_str())});
| ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\string.h:531:20: note: 'strdup' has been explicitly marked deprecated here
531 | Check_return _CRT_NONSTDC_DEPRECATE(_strdup)
| ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\corecrt.h:428:50: note: expanded from macro '_CRT_NONSTDC_DEPRECATE'
428 | #define _CRT_NONSTDC_DEPRECATE(_NewName) _CRT_DEPRECATE_TEXT(
| ^
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.44.35207\include\vcruntime.h:358:47: note: expanded from macro '_CRT_DEPRECATE_TEXT'
358 | #define _CRT_DEPRECATE_TEXT(_Text) __declspec(deprecated(_Text))
| ^
D:/a/llama.cpp/llama.cpp/examples/simple-chat/simple-chat.cpp:190:42: warning: 'strdup' is deprecated: The POSIX name for this item is deprecated. Instead, use the ISO C and C++ conformant name: _strdup. See online help for details. [-Wdeprecated-declarations]
190 | messages.push_back({"assistant", strdup(response.c_str())});
| ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\string.h:531:20: note: 'strdup' has been explicitly marked deprecated here
531 | Check_return _CRT_NONSTDC_DEPRECATE(_strdup)
| ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\corecrt.h:428:50: note: expanded from macro '_CRT_NONSTDC_DEPRECATE'
428 | #define _CRT_NONSTDC_DEPRECATE(_NewName) _CRT_DEPRECATE_TEXT(
| ^
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.44.35207\include\vcruntime.h:358:47: note: expanded from macro '_CRT_DEPRECATE_TEXT'
358 | #define _CRT_DEPRECATE_TEXT(_Text) __declspec(deprecated(_Text))
| ^
2 warnings generated.
[148/295] Linking CXX executable bin\Release\llama-gguf-hash.exe
clang++: warning: argument unused during compilation: '-fno-finite-math-only' [-Wunused-command-line-argument]
[149/295] Linking CXX shared library bin\Release\mtmd.dll
clang++: warning: argument unused during compilation: '-fno-finite-math-only' [-Wunused-command-line-argument]
[150/295] Linking C executable bin\Release\test-c.exe
clang: warning: argument unused during compilation: '-fno-finite-math-only' [-Wunused-command-line-argument]
[151/295] Linking CXX executable bin\Release\llama-simple.exe
clang++: warning: argument unused during compilation: '-fno-finite-math-only' [-Wunused-command-line-argument]
[152/295] Linking CXX executable bin\Release\llama-simple-chat.exe
clang++: warning: argument unused during compilation: '-fno-finite-math-only' [-Wunused-command-line-argument]
[153/295] Linking CXX executable bin\Release\llama-gguf.exe
clang++: warning: argument unused during compilation: '-fno-finite-math-only' [-Wunused-command-line-argument]
[154/295] Building OCI Go library
go: downloading github.com/google/go-containerregistry v0.20.6
go: downloading golang.org/x/term v0.36.0
go: downloading github.com/docker/cli v28.2.2+incompatible
go: downloading github.com/opencontainers/go-digest v1.0.0
go: downloading github.com/mitchellh/go-homedir v1.1.0
go: downloading golang.org/x/sync v0.15.0
go: downloading golang.org/x/sys v0.37.0
go: downloading github.com/docker/distribution v2.8.3+incompatible
go: downloading github.com/pkg/errors v0.9.1
go: downloading github.com/sirupsen/logrus v1.9.3
go: downloading github.com/opencontainers/image-spec v1.1.1
go: downloading github.com/containerd/stargz-snapshotter/estargz v0.16.3
go: downloading github.com/klauspost/compress v1.18.0
go: downloading github.com/docker/docker-credential-helpers v0.9.3
go: downloading github.com/vbatts/tar-split v0.12.1
[155/295] Building CXX object common/CMakeFiles/common.dir/Release/chat-parser.cpp.obj
[156/295] Building CXX object common/CMakeFiles/common.dir/Release/common.cpp.obj
[157/295] Building CXX object common/CMakeFiles/common.dir/Release/console.cpp.obj
[158/295] Building CXX object common/CMakeFiles/common.dir/Release/json-partial.cpp.obj
[159/295] Building CXX object common/CMakeFiles/common.dir/Release/llguidance...

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