[libc] Make the libc files always available to clang for the GPU (#100396)

Summary:
The GPU build always wants these to be exported to `clang`. These will
be neccesary for setting up tests or using the `libc` from the clang
binary. This will cover the standard 'runtimes' build. If the user is
doing a direct compilation, we will just leave it as-is and assume they
know what they're doing.

Test Plan: 

Reviewers: 

Subscribers: 

Tasks: 

Tags: 


Differential Revision: https://phabricator.intern.facebook.com/D60250688

Author: jhuber6

libc/CMakeLists.txt

@@ -228,7 +228,7 @@ foreach(config_path IN LISTS LIBC_CONFIG_JSON_FILE_LIST)
   load_libc_config(${config_path}/config.json ${cmd_line_conf})
 endforeach()
 
-if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND LIBC_ENABLE_USE_BY_CLANG)
+if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND (LIBC_ENABLE_USE_BY_CLANG OR LIBC_TARGET_OS_IS_GPU))
   set(LIBC_INCLUDE_DIR ${LLVM_BINARY_DIR}/include/${LLVM_DEFAULT_TARGET_TRIPLE})
   set(LIBC_INSTALL_INCLUDE_DIR ${CMAKE_INSTALL_INCLUDEDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})
   set(LIBC_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})
@@ -244,9 +244,7 @@ else()
     set(LIBC_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX})
   endif()
   if(LIBC_TARGET_OS_IS_GPU)
-    if(LLVM_RUNTIMES_TARGET)
-      set(LIBC_INSTALL_INCLUDE_DIR ${CMAKE_INSTALL_INCLUDEDIR}/${LLVM_RUNTIMES_TARGET})
-    elseif(LIBC_TARGET_TRIPLE)
+    if(LIBC_TARGET_TRIPLE)
       set(LIBC_INSTALL_INCLUDE_DIR ${CMAKE_INSTALL_INCLUDEDIR}/${LIBC_TARGET_TRIPLE})
     else()
       set(LIBC_INSTALL_INCLUDE_DIR ${CMAKE_INSTALL_INCLUDEDIR}/${LLVM_DEFAULT_TARGET_TRIPLE})