[CMake] Don't install c++abi headers in standalone libc++ build

This is a refinement on r337833. Previously we were installing two
copies of c++abi headers in libc++ build directory, one in
include/c++build and another one in include/c++/v1. However, the
second copy is unnecessary when building libc++ standalone.

Differential Revision: https://reviews.llvm.org/D49752

llvm-svn: 337979

libcxx/CMakeLists.txt

@@ -407,7 +407,6 @@ elseif(LLVM_LIBRARY_OUTPUT_INTDIR)
   set(LIBCXX_HEADER_DIR  ${LLVM_BINARY_DIR})
 else()
   set(LIBCXX_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LIBCXX_LIBDIR_SUFFIX})
-  set(LIBCXX_HEADER_DIR  ${CMAKE_BINARY_DIR})
 endif()
 
 file(MAKE_DIRECTORY "${LIBCXX_BINARY_INCLUDE_DIR}")

libcxx/cmake/Modules/HandleLibCXXABI.cmake

@@ -48,7 +48,7 @@ macro(setup_abi_lib abidefines abilib abifiles abidirs)
             COMMENT "Copying C++ ABI header ${fpath}...")
         list(APPEND abilib_headers "${dst}")
 
-        if (NOT LIBCXX_USING_INSTALLED_LLVM)
+        if (NOT LIBCXX_USING_INSTALLED_LLVM AND LIBCXX_HEADER_DIR)
           set(dst "${LIBCXX_HEADER_DIR}/include/c++/v1/${dstdir}/${fpath}")
           add_custom_command(OUTPUT ${dst}
               DEPENDS ${src}

libcxx/include/CMakeLists.txt

@@ -205,7 +205,7 @@ else()
     )
 endif()
 
-if(NOT LIBCXX_USING_INSTALLED_LLVM AND LLVM_BINARY_DIR)
+if(NOT LIBCXX_USING_INSTALLED_LLVM AND LIBCXX_HEADER_DIR)
   set(output_dir ${LIBCXX_HEADER_DIR}/include/c++/v1)
 
   set(out_files)