Linux 7.2 To Raise LLVM/Clang Compiler Requirement, Add Support For Distributed ThinLTO

Linux 7.2 will raise the minimum LLVM/Clang compiler requirement from Clang 15 to Clang 17 when building the kernel with LLVM. The bump aligns Clang capabilities more closely with GCC, resolving scope checker issues and const variable compatibility with _static_assert. Additionally, Linux 7.2 adds support for LLVM's Distributed ThinLTO (DTLTO) mode, which enables faster kernel builds compared to in-process ThinLTO. Other Kbuild changes include hardening Kconfig against null pointer dereferences, a new kconfig-sym-check target for dangling symbol references, and various typo fixes.