Why is Linux support disabled in the XR gems?

[ChristophHaag]

I'm not familiar with o3de, but wanted to see if the XR support worked on Linux. So I installed the 24.09.0 binary version of o3de on archlinux

Creating a new project with the downloaded XR gems from the asset library predictably didn't launch any XR mode when going into play mode with ctrl+g, so I deleted the downloaded gems in the Gem directory and tried to add the ones from an o3de-extras checkout of the 2409.0 branch but other than outputting 1.12.1 these commands do nothing:

$ /opt/O3DE/24.09/scripts/o3de.sh register -gp /home/haagch/o3de-extras/Gems/XR -espp /home/haagch/O3DE/Projects/OpenXRTest/1.0.1
1.12.1
$ /opt/O3DE/24.09/scripts/o3de.sh register -gp /home/haagch/o3de-extras/Gems/OpenXRVk -espp /home/haagch/O3DE/Projects/OpenXRTest/1.0.1
1.12.1 

so I just went ahead and added them manually in my project in project.json

    "external_subdirectories": [
        "Gem",
        "/home/haagch/o3de-extras/Gems/XR",
        "/home/haagch/o3de-extras/Gems/OpenXRVk"
    ],

Now to the gem code.

First I see this commit but I could not find any rationale to why: 6001b28

Once I revert that commit and click build in the editor, it hits this error #error "Linux Window Manager not recognized." https://github.com/o3de/o3de-extras/blob/2409.0/Gems/OpenXRVk/Code/Include/OpenXRVk/Platform/Linux/OpenXRVk_Linux.h#L17-L24

afaik you only support OpenXR with the Vulkan RHI, which has no need for any interaction with xlib/xcb or wayland (the wayland graphics binding really shouldn't exist in this form anyway). So once I delete these ifdefs and hit build again, I am hit with a less clear linking error

[1/13] Linking CXX static library lib/profile/libXR.Static.a
[2/13] Copying XR runtime dependencies to output...
[3/13] Building CXX object External/XR-d0652409/Code/CMakeFiles/XR.dir/profile/Unity/unity_0_cxx.cxx.o
[4/13] Linking CXX shared module bin/profile/libXR.so
FAILED: bin/profile/libXR.so 
: && /usr/sbin/clang++ -fPIC -fno-exceptions -fvisibility=hidden -fvisibility-inlines-hidden -Wall -Werror -Wno-inconsistent-missing-override -Wrange-loop-analysis -Wno-unknown-warning-option -Wno-parentheses -Wno-reorder -Wno-switch -Wno-undefined-var-template -msse4.1  -O2 -g -fstack-protector-all -fstack-check  -Wl,--no-undefined -fpie -Wl,-z,relro,-z,now -Wl,-z,noexecstack -shared  -o bin/profile/libXR.so External/XR-d0652409/Code/CMakeFiles/XR.dir/profile/Unity/unity_0_cxx.cxx.o  -Wl,-rpath,"\$ORIGIN"  lib/profile/libXR.Static.a  /opt/O3DE/24.09/lib/Linux/profile/Default/libAtom_RPI.Public.a  /opt/O3DE/24.09/lib/Linux/profile/Default/libAtom_RHI.Public.a  /opt/O3DE/24.09/lib/Linux/profile/Default/libAtom_RHI.Reflect.a  /opt/O3DE/24.09/lib/Linux/profile/Default/libAzFramework.a  /opt/O3DE/24.09/lib/Linux/profile/Default/libAzNetworking.a  /home/haagch/.o3de/3rdParty/packages/OpenSSL-1.1.1t-rev1-linux/OpenSSL/lib/libssl.a  /home/haagch/.o3de/3rdParty/packages/OpenSSL-1.1.1t-rev1-linux/OpenSSL/lib/libcrypto.a  /home/haagch/.o3de/3rdParty/packages/lz4-1.9.4-rev2-linux/lz4/lib/liblz4.a  /opt/O3DE/24.09/lib/Linux/profile/Default/libAtomCore.a  /opt/O3DE/24.09/lib/Linux/profile/Default/libAzCore.a  /home/haagch/.o3de/3rdParty/packages/Lua-5.4.4-rev1-linux/Lua/lib/release/liblualib.a  /home/haagch/.o3de/3rdParty/packages/zlib-1.2.11-rev5-linux/zlib/lib/libz.a  /usr/lib/libzstd.so  /home/haagch/.o3de/3rdParty/packages/cityhash-1.1-multiplatform/cityhash/build/linux/clang-3.8/release/libcityhash.a  /opt/O3DE/24.09/bin/Linux/profile/Default/./libO3DEKernel.so  -ldl  -lpthread  /usr/lib/libunwind.so  -latomic && cd /home/haagch/O3DE/Projects/openxrtest/build/linux/External/XR-d0652409/Code && /usr/bin/cmake -P /opt/O3DE/24.09/cmake/Platform/Linux/ProcessDebugSymbols.cmake /usr/bin/strip /usr/bin/objcopy /home/haagch/O3DE/Projects/openxrtest/build/linux/bin/profile/libXR.so dbg MODULE_LIBRARY DETACH
/usr/sbin/ld: lib/profile/libXR.Static.a(unity_0_cxx.cxx.o): in function `AZ::AzTypeInfo<AZStd::basic_fixed_string<char, 256ul, AZStd::char_traits<char> > >::GetCanonicalTypeId()':
/opt/O3DE/24.09/Code/Framework/AzCore/./AzCore/RTTI/TypeInfoSimple.h:317:(.text.startup[_ZN2XR39r_default_openxr_foveated_pass_templateE]+0x144): undefined reference to `_ZN5AZStd13GetO3deTypeIdIcTnDaLm256ENS_11char_traitsIcEEEEN2AZ4UuidENS3_3AdlENS_13type_identityINS_18basic_fixed_stringIT_XT0_ET1_EEEE'

might this be because of differences in the debian build and clang 18.1.8 from archlinux?