Update google-benchmark to 1.7.0

[AreaZR]

Additionally makes benchmarks separate from the STL build, since we keep having problems when google benchmark is built in the STL build.

[StephanTLavavej]

@strega-nil-ms will investigate why the build is failing.

[strega-nil-ms]

It looks like there is a bug in google benchmark that means we can't update for now:

std_copy.cpp.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl benchmark::internal::FunctionBenchmark::FunctionBenchmark(char const *,void (__cdecl*)(class benchmark::State &))" (__imp_??0FunctionBenchmark@internal@benchmark@@QEAA@PEBDP6AXAEAVState@2@@Z@Z) referenced in function "void __cdecl `dynamic initializer for 'benchmark_uniq_10std_copy_call''(void)" (??__Ebenchmark_uniq_10std_copy_call@@YAXXZ)
std_copy.cpp.obj : error LNK2019: unresolved external symbol "__declspec(dllimport) public: virtual __cdecl benchmark::internal::FunctionBenchmark::~FunctionBenchmark(void)" (__imp_??1FunctionBenchmark@internal@benchmark@@UEAA@XZ) referenced in function "public: virtual void * __cdecl benchmark::internal::FunctionBenchmark::`scalar deleting destructor'(unsigned int)" (??_GFunctionBenchmark@internal@benchmark@@UEAAPEAXI@Z)
benchmark-std_copy.exe : fatal error LNK1120: 2 unresolved externals

Edit: See google/benchmark#1450; there is a workaround.

[barcharcraz]

I'm not 100% convinced separating out the benchmark build is an improvement. Our main build is a bit of an oddball though.

[strega-nil-ms]

@barcharcraz there were multiple problems caused by having google benchmark as part of the main build (like, in google benchmark's build system); splitting it out removed those problems. I would prefer not to if there weren't those issues, but I also don't think creating workarounds is worth making the benchmark part of the main build.

[StephanTLavavej]

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

[StephanTLavavej]

Thanks @AtariDreams for updating this dependency and @strega-nil-ms for reworking the build system! ✅ 🚀 🎉