cmake: conditionally enable ASM via check_language to fix MSVC/CMake configuration failures

[turbolego]

Overview

This PR fixes a Windows/MSVC configuration failure in ggml caused by unconditional enabling of the ASM language in CMake.

On modern CMake versions (CMake 4.x / CMP0194 policy behavior), MSVC is not reliably treated as a valid ASM compiler. This leads to early configuration failures such as:

• "No CMAKE_ASM_COMPILER could be found"
• "The ASM compiler identification is unknown"

even when a fully functional Visual Studio toolchain is present.

To address this, ASM support is now enabled conditionally using check_language(ASM), and only activated when the toolchain actually supports it. On MSVC, ASM is skipped while remaining enabled for toolchains where it is supported (GNU, Clang, NASM, etc.).

This preserves ASM optimizations where available while fixing Windows/MSVC build reliability issues without globally disabling ASM.

---

Additional information

This change avoids forcing ASM via:

project("ggml" C CXX ASM)

Instead, ASM is now enabled only when CMake confirms support:

include(CheckLanguage)

check_language(ASM)
if (CMAKE_ASM_COMPILER AND NOT MSVC)
    enable_language(ASM)
endif()

project("ggml" C CXX)

Why this is needed

Recent CMake versions changed ASM handling under policy CMP0194:

• MSVC is no longer considered a valid ASM compiler candidate
• enable_language(ASM) may fail early in configuration
• Projects that unconditionally enable ASM can break even without using assembly sources

Since ggml does not require ASM for CUDA / CPU builds on Windows, disabling ASM conditionally avoids breaking configuration while keeping ASM support intact on supported toolchains.

Impact

• Fixes Windows/MSVC configuration failures
• Preserves ASM optimizations on Linux/macOS/other toolchains
• No runtime behavior changes
• CUDA and CPU backends are unaffected

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: AI was used to draft, tested manually by me before submission.