The cmake script is failing to copy cxxabi.h to the right place because it was generating to destination path like so /include// and dstdir can legally be blank from my interpretation of the script, and this would then generate a path like libcxx/include// which is illegal.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@178579 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -106,7 +106,7 @@ macro(setup_abi_lib abipathvar abidefines abilibs abifiles abidirs)
           OUTPUT "${CMAKE_BINARY_DIR}/include/${dstdir}/${ifile}"
           COMMAND ${CMAKE_COMMAND} -E copy_if_different
             "${incpath}/${fpath}"
-            "${CMAKE_BINARY_DIR}/include/${dstdir}/"
+            "${CMAKE_BINARY_DIR}/include/${dstdir}"
           MAIN_DEPENDENCY "${incpath}/${fpath}"
           )
         list(APPEND LIBCXX_CXX_ABI_DEPS