Fix linker script generation for in-tree builds

llvm-svn: 283700
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 054fc4cef621e1cea0b2dd754f8f9e17b5097353
diff --git a/cmake/Modules/HandleLibcxxFlags.cmake b/cmake/Modules/HandleLibcxxFlags.cmake
index 325c1bd..7077c6e 100644
--- a/cmake/Modules/HandleLibcxxFlags.cmake
+++ b/cmake/Modules/HandleLibcxxFlags.cmake
@@ -188,6 +188,14 @@
   endif()
 endmacro()
 
+# Add a list of libraries or link flags to 'LIBCXX_LIBRARIES'.
+macro(add_interface_library)
+  foreach(lib ${ARGN})
+    list(APPEND LIBCXX_LIBRARIES ${lib})
+    list(APPEND LIBCXX_INTERFACE_LIBRARIES ${lib})
+  endforeach()
+endmacro()
+
 # Turn a comma separated CMake list into a space separated string.
 macro(split_list listname)
   string(REPLACE ";" " " ${listname} "${${listname}}")