[libclc] [libclc] Fix installation w/ ENABLE_RUNTIME_SUBNORMAL (PR #109926)

[Fraser Cormack via cfe-commits]

================
@@ -221,8 +221,10 @@ if( ENABLE_RUNTIME_SUBNORMAL )
        TARGET ${file}
        INPUTS ${CMAKE_CURRENT_SOURCE_DIR}/generic/lib/${file}.ll
     )
-    install( FILES $<TARGET_PROPERTY:${file},TARGET_FILE> ARCHIVE
-      DESTINATION "${CMAKE_INSTALL_DATADIR}/clc" )
+    install(
+      FILES ${CMAKE_CURRENT_BINARY_DIR}/$<TARGET_PROPERTY:${file},TARGET_FILE>
----------------
frasercrmck wrote:

It doesn't appear to work

```
  Target "subnormal_disable" is not an executable or library.
```

I think this section of the documentation alludes to this:

``` quote
These expressions look up information about artifacts associated with a given target tgt. Unless otherwise stated, this can be any runtime artifact, namely:

  * An executable target created by add_executable().
  * A shared library target (.so, .dll but not their .lib import library) created by add_library().
  * A static library target created by add_library().
```

These files are created by `add_custom_command`. That might be why we create our own `TARGET_FILE` property on these targets, to mimic this built-in `TARGET_FILE` behaviour?

https://github.com/llvm/llvm-project/pull/109926