[clang][SYCL] Fix compilation of MSVC headers (#22154)
MSVC headers rely heavily on __cdecl calling convention attribute. SYCL
device mosly uses SPIR-based targets which use spir_function default
calling convention not compatible with __cdecl. I've made an attempt to
avoid errors coming from MSVC headers using CUDA-style approach in
94ca49099ef77751a33e4babe41b2ae03ff228e1 which however failed for
several reasons. Most this happens because SYCL is implicit about what
is compiled for device and it allows to include standard C++ headers
during device compilations, so the approach that was taken in
94ca49099ef77751a33e4babe41b2ae03ff228e1 didn't work for the two more
cases in MSVC headers:
1. allocation/deallocation functions are marked with __cdecl and that
was conflicting with implicit declarations of these with default calling
convention.
2. due to 94ca49099ef77751a33e4babe41b2ae03ff228e1 applied, __cdecl
calling covention attribute was preserved on functions even though it is
not supported for the target and it declares different calling
convention than the default that caused function types for functions
with and without __cdecl attribute to be different and cause fail to
compile MSVC headers.
This is to unblock the pulldown but I'm going to propose this to the
community as well since SYCL language design doesn't give us another way
to solve this.
