[HLSL] [SPIRV] Don't generate per-variable guards for SPIR-V with HLSL

[pow2clk]

Thread init guards are generated for local static variables when using the Itanium CXX ABI. This ABI is also used for SPIRV generation, but at least for HLSL targets doesn't need the corresponding __cxa_guard_acquire/release calls and doesn't really have a way to handle them in its output targets.

Similar to what this PR does, but for SPIR-V #106096

[llvmbot]

@llvm/issue-subscribers-clang-codegen

Author: Greg Roth (pow2clk)

Thread init guards are generated for local static variables when using the Itanium CXX ABI. This ABI is also used for SPIRV generation, but at least for HLSL targets doesn't need the corresponding `__cxa_guard_acquire/release` calls and doesn't really have a way to handle them in its output targets.

Similar to what this PR does, but for SPIR-V #106096