[CMake] Stop symlinking build/llvm/lib into build/swift/lib/swift/ (swiftlang#15458)

We started doing this to test out libFuzzer, but that's now available
through the usual sanitizer interface, and it turns out this symlink
is actually harmful because it causes the llvm/lib/ folder to get
copied into the built LLDB framework, and it contains all sorts of
garbage intermediate files (static libraries and such). On my machine
it was an extra 9GB for no reason.

Anyway, we're not using this anymore, so take it out. I suggest
clearing out build/lib/swift/ after this change too.

Author: jrose-apple

stdlib/public/SwiftShims/CMakeLists.txt

@@ -101,12 +101,10 @@ function(find_llvm_clang_headers suffix description out_var)
 endfunction()
 
 if(SWIFT_BUILT_STANDALONE)
-  find_llvm_clang_headers("" "LLVM" llvm_headers_location)
   find_llvm_clang_headers("/clang/${CLANG_VERSION}" "Clang"
     clang_headers_location)
 else() # NOT SWIFT_BUILT_STANDALONE
   set(clang_headers_location "${LLVM_LIBRARY_DIR}/clang/${CLANG_VERSION}")
-  set(llvm_headers_location "${LLVM_LIBRARY_DIR}")
 endif()
 
 if("${CMAKE_SYSTEM_NAME}" STREQUAL "Windows")
@@ -126,20 +124,7 @@ add_custom_command_target(unused_var
     CUSTOM_TARGET_NAME "symlink_clang_headers"
     OUTPUT "${SWIFTLIB_DIR}/clang"
     COMMENT "Symlinking Clang resource headers into ${SWIFTLIB_DIR}/clang")
-
-# Adding LLVM symlink at compile time.
-add_custom_command_target(unused_var2
-    COMMAND
-      "${CMAKE_COMMAND}" "-E" "make_directory" "${SWIFTLIB_DIR}"
-    COMMAND
-      "${CMAKE_COMMAND}" "-E" "${cmake_symlink_option}"
-      "${llvm_headers_location}"
-      "${SWIFTLIB_DIR}/llvm"
-
-    CUSTOM_TARGET_NAME "symlink_llvm_headers"
-    OUTPUT "${SWIFTLIB_DIR}/llvm"
-    COMMENT "Symlinking LLVM resource headers into ${SWIFTLIB_DIR}/llvm")
-add_dependencies(copy_shim_headers symlink_clang_headers symlink_llvm_headers)
+add_dependencies(copy_shim_headers symlink_clang_headers)
 
 swift_install_in_component(compiler
     FILES ${sources}