Don't use <intrin0.h> with Clang

[CaseyCarter]

Addresses the problem mentioned in #2520 (comment). We've had several issues with Clang and intrin0.h in the past, hopefully we can fix them "forever" by avoiding intrin0.h when compiling with Clang.

The existence of intrin0.h is purely an optimization in that it allows us to avoid including the entirety of intrin.h. We could support this optimization with Clang in the future by adding an intrin0.h to Clang's set of override headers. If we were to do so we should synchronize with libc++ on the proper set of intrinsics to move into intrin0.h.

[StephanTLavavej]

Looks good, I've pushed a tiny change to remove fine-grained header inclusion since we're using the coarse-grained header in src/vector_algorithms.cpp. FYI @strega-nil-ms as you already approved.

There is one remaining occurrence of us including something smaller than intrin.h:

STL/stl/inc/complex

Lines 25 to 29 in 4483e87

	#elif defined(__clang__) // ^^^ defined(_M_ARM64) || defined(_M_ARM64EC) ^^^
	// TRANSITION, not using x86/x64 FMA intrinsics for Clang yet
	#elif defined(_M_IX86) || defined(_M_X64)
	#define _FMP_USING_X86_X64_INTRINSICS
	#include <emmintrin.h>

This currently excludes Clang and is special, so leaving it as-is is totally fine.

[CaseyCarter]

There is one remaining occurrence of us including something smaller than intrin.h:

[code that includes emmintrin.h]

This would be fine: Clang overrides many (all?) of the Intel intrinsic headers. intrin0.h is a problem only because it's a header that we "made up" which Clang doesn't override.

[StephanTLavavej]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[StephanTLavavej]

Thanks for noticing the repeated problems here and finding a robust way to avoid them forever! 🛠️ 🐈 🎉

[Kojoley]

This quite dramatically increased inclusion cost for a lot of headers:

msvc	clang was	clang now	slow down	header
0.068	0.082	0.369	351%	<limits>
0.093	0.101	0.387	284%	<atomic>
0.097	0.103	0.389	277%	<latch>
0.102	0.110	0.396	259%	<bit>
0.111	0.126	0.410	226%	<compare>
0.119	0.133	0.424	219%	<coroutine>
0.119	0.134	0.419	213%	<utility>
0.120	0.134	0.419	212%	<typeindex>
0.141	0.155	0.448	189%	<tuple>
0.179	0.206	0.491	139%	<array>
0.178	0.207	0.493	138%	<span>
0.180	0.207	0.491	137%	<numeric>
0.185	0.215	0.499	132%	<iterator>
0.195	0.222	0.511	131%	<semaphore>
0.191	0.219	0.504	130%	<expected>
0.193	0.229	0.513	124%	<cmath>
0.213	0.243	0.528	117%	<scoped_allocator>
0.217	0.245	0.530	116%	<any>
0.222	0.250	0.535	114%	<deque>
0.219	0.249	0.532	114%	<forward_list>
0.221	0.250	0.533	113%	<optional>
0.231	0.264	0.560	112%	<list>
0.226	0.258	0.539	109%	<set>
0.229	0.262	0.546	109%	<vector>
0.229	0.260	0.541	108%	<map>
0.245	0.283	0.576	104%	<barrier>
0.243	0.278	0.563	102%	<stop_token>
0.255	0.301	0.595	97%	<valarray>
0.258	0.299	0.582	95%	<charconv>
0.266	0.307	0.589	92%	<memory>
0.271	0.319	0.602	89%	<unordered_set>
0.287	0.328	0.620	89%	<variant>
0.272	0.319	0.603	89%	<unordered_map>
0.300	0.328	0.613	87%	<string_view>
0.302	0.330	0.614	86%	<stdexcept>
0.302	0.332	0.618	86%	<bitset>
0.296	0.343	0.626	83%	<functional>
0.300	0.345	0.629	82%	<algorithm>
0.319	0.351	0.634	81%	<string>
0.321	0.358	0.643	80%	<thread>
0.342	0.371	0.655	77%	<system_error>
0.359	0.397	0.685	72%	<stacktrace>
0.438	0.480	0.774	61%	<streambuf>
0.444	0.476	0.761	60%	<shared_mutex>
0.434	0.471	0.753	60%	<mutex>
0.441	0.476	0.759	59%	<condition_variable>
0.459	0.511	0.798	56%	<ios>
0.416	0.506	0.789	56%	<ranges>
0.424	0.518	0.799	54%	<stack>
0.505	0.528	0.811	54%	<memory_resource>
0.481	0.541	0.826	52%	<codecvt>
0.511	0.539	0.820	52%	<locale>
0.533	0.649	0.939	45%	<queue>
0.654	0.764	1.056	38%	<random>
0.666	0.762	1.048	38%	<format>
0.692	0.787	1.075	37%	<fstream>
0.691	0.788	1.075	37%	<syncstream>
0.724	0.824	1.121	36%	<iomanip>
0.689	0.787	1.070	36%	<istream>
0.658	0.794	1.079	36%	<regex>
0.693	0.790	1.073	36%	<spanstream>
0.714	0.803	1.089	36%	<sstream>
0.690	0.787	1.066	35%	<iostream>
0.731	0.833	1.125	35%	<strstream>
0.766	0.866	1.166	35%	<complex>
0.684	0.827	1.112	35%	<ostream>
0.807	0.853	1.143	34%	<print>
0.725	0.870	1.152	32%	<execution>
1.117	1.238	1.520	23%	<chrono>
1.388	1.512	1.795	19%	<filesystem>
2.528	2.914	2.868	-2%	<__msvc_all_public_headers.hpp>