Hi All,

Environment:
VS 2019 + Windows Server 2019

Rapidyaml failed to build due to fatal error C1189: #error: "unknown endianness" with MSVC on windows arm64. It can be reproduced on latest version ed547aa on master branch. Could you please help look at this issue? Does Rapidyaml support windows arm64?

ARM64_build_log:
build_arm64.zip

Repro steps:

1. git clone https://github.com/biojppm/rapidyaml F:\gitP\biojppm\rapidyaml
2. cd F:\gitP\biojppm\rapidyaml && git -C "F:\gitP\biojppm\rapidyaml" submodule update --init --recursive
3. mkdir build_arm64 && cd build_arm64
4. cmake -G "Visual Studio 16 2019" -A arm64 -DCMAKE_SYSTEM_VERSION=10.0.18362.0 -DRYML_BUILD_TESTS=ON -DCMAKE_INSTALL_PREFIX=install/dir ..
5. msbuild /m /p:Platform=arm64 /p:Configuration=Release ryml.sln /t:Rebuild

Error info:
62>F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4/cpu.hpp(79,1): fatal error C1189: #error: "unknown endianness" [F:\gitP\biojppm\rapidyaml\build_arm64\ryml.vcxproj]
64>ClCompile:
log.cpp
62>ClCompile:
node.cpp
65>F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4/cpu.hpp(79,1): fatal error C1189: #error: "unknown endianness" [F:\gitP\biojppm\rapidyaml\build_arm64\subprojects\c4fs\build\c4fs.vcxproj]
66>ClCompile:
C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.29.30133\bin\HostX64\arm64\CL.exe /c /IF:\gitP\biojppm\rapidyaml\ext\c4core\src /nologo /W3 /WX- /diagnostics:column /O2 /Ob2 /Oy- /D _ARM64_WINAPI_PARTITION_DESKTOP_SDK_AVAILABLE=1 /D _MBCS /D WIN32 /D _WINDOWS /D NDEBUG /D "CMAKE_INTDIR="Release"" /Gm- /EHsc /MD /GS /fp:precise /Zc:wchar_t /Zc:forScope /Zc:inline /GR /Fo"c4core.dir\Release\" /Fd"F:\gitP\biojppm\rapidyaml\build_arm64\subprojects\c4core\build\Release\c4core.pdb" /external:W3 /Gd /TP /analyze- /errorReport:queue F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4\base64.cpp F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4\char_traits.cpp F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4\error.cpp F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4\format.cpp F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4\language.cpp F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4\memory_resource.cpp F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4\memory_util.cpp F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4\utf.cpp
65>ClCompile:
base64.cpp
62>F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4/cpu.hpp(79,1): fatal error C1189: #error: "unknown endianness" [F:\gitP\biojppm\rapidyaml\build_arm64\ryml.vcxproj]
parse.cpp
62>F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4/cpu.hpp(79,1): fatal error C1189: #error: "unknown endianness" [F:\gitP\biojppm\rapidyaml\build_arm64\ryml.vcxproj]
preprocess.cpp
66>ClCompile:
base64.cpp
62>F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4/cpu.hpp(79,1): fatal error C1189: #error: "unknown endianness" [F:\gitP\biojppm\rapidyaml\build_arm64\ryml.vcxproj]
tree.cpp
65>F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4/cpu.hpp(79,1): fatal error C1189: #error: "unknown endianness" [F:\gitP\biojppm\rapidyaml\build_arm64\subprojects\c4fs\build\c4fs.vcxproj]
char_traits.cpp
64>F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4/cpu.hpp(79,1): fatal error C1189: #error: "unknown endianness" [F:\gitP\biojppm\rapidyaml\build_arm64\test\subprojects\c4log\build\c4log.vcxproj]
base64.cpp
62>F:\gitP\biojppm\rapidyaml\ext\c4core\src\c4/cpu.hpp(79,1): fatal error C1189: #error: "unknown endianness" [F:\gitP\biojppm\rapidyaml\build_arm64\ryml.vcxproj]