[cmake] Provide an option to not install the support headers so that the cmake build can match the make build if requested.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@189739 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CMakeLists.txt

@@ -100,9 +100,15 @@ install(TARGETS cxx
   ARCHIVE DESTINATION lib
   )
 
+
+if (NOT LIBCXX_INSTALL_SUPPORT_HEADERS)
+  set(LIBCXX_SUPPORT_HEADER_PATTERN PATTERN "support" EXCLUDE)
+endif()
+
 install(DIRECTORY ../include/
   DESTINATION include/c++/v1
   FILES_MATCHING
   PATTERN "*"
   PATTERN ".svn" EXCLUDE
+  ${LIBCXX_SUPPORT_HEADER_PATTERN}
   )