Feature Request: SYCL build: file-local functions missing static, unreachable code after abort, extra semicolons #30269

Prerequisites

• I am running the latest code. Mention the version if possible as well.
• I carefully followed the README.md.
• I searched using keywords relevant to my issue to make sure that I am creating a new issue that is not already open (or closed).
• I reviewed the Discussions, and have a new and useful enhancement to share.

Feature Description

This isn't a such much a feature request, but an request to add an enhancement / update to the cmake build system. And the second part is a clean-up of warning messages.

Motivation

The current Intel oneAPI DPC++ and I believe intel/llvm (sycl branch) identify as IntelLLVM not as Clang in CMake's CMAKE_COMPILER_ID, which means that the default warnings are not configured for some/many SYCL builds.

Secondly, as a result of adding these warnings to the IntelLLVM based builds, the usual warning set (-Wall -Wextra -Wpedantic -Wmissing-prototypes -Wextra-semi) surfaces a number of small, pre-existing hygiene issues in ggml/src/ggml-sycl/. None are functional bugs; all are behaviour-preserving cleanups:

• File-local helpers defined without static and with no prior
  declaration (flagged by -Wmissing-prototypes, which IntelLLVM applies to
  C++ and mainline Clang does not):

Each is only referenced in its own file, the surrounding helpers in the same files are already static, so this matches the existing pattern.

One exception is ggml_sycl_op_dated_linear_attn is called from ggml-sycl.cpp, so it is fixed by including the gla.hpp header that already declares it.

• Unreachable break; / return; immediately after a noreturn call
  (GGML_ABORT / GGML_ASSERT(false); ggml_abort is GGML_NORETURN):
  concat, count-equal, fattn-tile, getrows, topk-moe, ggml-sycl (x2),
  convert (x3).
• Extra semicolon ; after a function / member definition: upscale (x3),
  vecdotq (x1), and in dpct/helper.hpp.
• fattn-common - replace deprecated parallel_for(properties) overload
• fattn-common - express reqd_sub_group_size as a kernel property

Changes are split across files in case there any issues or concerns.

Possible Implementation

I will submit an PR of my draft for these issues. PR #30271

I welcome comments, constructive criticism, and feedback.