[Bug]: Windows ARM64 (MSVC): ailego CMake returns early and never creates zvec_ailego

[ahmedSamir50]

Description

Configuring zvec for Windows ARM64 with MSVC fails at CMake configure (before any compile of zvec_c_api).

src/ailego/CMakeLists.txt enters the ARM path correctly (HOST_ARCH matches arm|arm64), then does:

elseif (HOST_ARCH MATCHES ^(arm|arm64)$)
    if(MSVC)
        return()
    endif()
    set(MATH_MARCH_FLAG_NEON -march=armv8-a)
    ...
endif()

cc_library(
    NAME zvec_ailego STATIC STRICT PACKED
    ...
)

The return() exits this CMakeLists before cc_library, so target zvec_ailego is never created.

Meanwhile src/CMakeLists.txt still has BUILD_ZVEC_AILEGO_SHARED=ON (default) and calls zvec_add_all_in_one_shared(zvec_ailego_shared ... LIBS zvec_ailego), which fatals:

CMake Error at src/CMakeLists.txt:31 (message):
  Target zvec_ailego is required by zvec_ailego_shared

So ARM64 itself works for non-MSVC compilers; MSVC ARM64 is aborted without disabling the shared target that depends on ailego.

Contrast (same zvec pin, same CI matrix)

On the same desktop native workflow:

Target	Compiler	Result
linux-arm64	GCC/Clang	success
osx-arm64 (Apple Silicon)	AppleClang	success
win-arm64	MSVC	configure FATAL above

All three hit HOST_ARCH arm/arm64; only MSVC hits return().

Public job: https://github.com/ahmedSamir50/AdamSystems.ZVec.NET/actions/runs/30286685888/job/90046139977

Steps to Reproduce

On Windows with the MSVC arm64 toolset (x64 host → arm64 target is enough; a native Windows ARM MSVC build should hit the same return()):

cmake -B build -G Ninja ^
  -DCMAKE_SYSTEM_NAME=Windows ^
  -DCMAKE_SYSTEM_PROCESSOR=ARM64 ^
  -DBUILD_C_BINDINGS=ON ^
  -DBUILD_ZVEC_AILEGO_SHARED=ON

Configure ends with Target zvec_ailego is required by zvec_ailego_shared.

Log excerpts from CI:

-- BUILD_ZVEC_AILEGO_SHARED:ON
-- turbo: ARM64 detected, skipping x86-specific optimizations
CMake Error at external/zvec/src/CMakeLists.txt:31 (message):
  Target zvec_ailego is required by zvec_ailego_shared
-- Configuring incomplete, errors occurred!

Suggested fix

1. Preferred: Remove the MSVC return() and wire MSVC-compatible ARM64 / NEON flags (instead of GCC-style -march=armv8-a) so cc_library(zvec_ailego) still runs on MSVC ARM64.
2. Or, if MSVC ARM64 ailego is intentionally unsupported for now: emit a clear error and turn off BUILD_ZVEC_AILEGO_SHARED / skip zvec_add_all_in_one_shared when the static target was not created (do not FATAL after silently skipping the library).

A silent return() that leaves the shared graph enabled is what bites consumers.

Additional Context

• zvec ~0.5.1 (C bindings / all-in-one shared defaults).
• Hit while packaging the C API for .NET (AdamSystems.ZVec.NET); host win64 protoc was injected correctly — failure is earlier, in ailego CMake.
• Ruled out binding / runtime teardown (not [Bug]: Linux SIGSEGV (exit 139) on zvec_collection_close / zvec_shutdown after successful create_and_open #619-class): this is configure-only; managed code never runs. Linux and Apple Silicon ARM64 natives on the same matrix are green.
• Happy to test a PR.

Operating System

Windows (MSVC arm64 toolset; CI: windows-2025 x64 host + amd64→arm64 cross).

Build & Runtime Environment

• Generator: Ninja
• Compiler: MSVC 19.51.x (Hostx64/arm64)
• Flags: -DCMAKE_SYSTEM_NAME=Windows -DCMAKE_SYSTEM_PROCESSOR=ARM64, BUILD_C_BINDINGS=ON, BUILD_ZVEC_AILEGO_SHARED=ON