[llvm] [OFFLOAD] Add level_zero to list of default plugins (PR #210070)

[Nick Sarnie via llvm-commits]

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@@ -144,7 +144,7 @@ if(DEFINED LIBOMPTARGET_BUILD_CUDA_PLUGIN OR
 endif()
 
 if(WIN32)
-  set(LIBOMPTARGET_ALL_PLUGIN_TARGETS "")
+  set(LIBOMPTARGET_ALL_PLUGIN_TARGETS level_zero)
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sarnex wrote:

it's true most of the remaining issues seem to be somewhere in spirv and not in the plugin, but from the user pov if they try to use the plugin (through spirv since that's all we support), it's likely to not work. 

i'm not sure what the usability expectation is for a plugin being enabled by default, so it's fine with me, but let's wait for other opinions

https://github.com/llvm/llvm-project/pull/210070