[llvm] [Libomptarget] Rework interface for enabling plugins (PR #86875)

[Johannes Doerfert via llvm-commits]

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@@ -151,6 +151,25 @@ if (NOT LIBOMPTARGET_LLVM_INCLUDE_DIRS)
   message(FATAL_ERROR "Missing definition for LIBOMPTARGET_LLVM_INCLUDE_DIRS")
 endif()
 
+set(LIBOMPTARGET_ALL_PLUGIN_TARGETS amdgpu cuda host)
+set(LIBOMPTARGET_PLUGINS_TO_BUILD "all" CACHE STRING
+    "Semicolon-separated list of plugins to use, or \"all\".")
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jdoerfert wrote:

list the plugin names.

https://github.com/llvm/llvm-project/pull/86875