Replace iwyu rules for libcxx with reference to rules maintain by the library

No-Try: True
Bug: None
Change-Id: Ie79dbb1fd5e0b544ca0ea41a58eabd1967e7d5e7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/285481
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38766}
diff --git a/tools_webrtc/iwyu/mappings.imp b/tools_webrtc/iwyu/mappings.imp
index fa111fa..a79997b 100644
--- a/tools_webrtc/iwyu/mappings.imp
+++ b/tools_webrtc/iwyu/mappings.imp
@@ -32,11 +32,7 @@
 { symbol: ["std::unique_ptr", "public", "<memory>", "public"] },
 # Needed to avoid <iosfwd>
 { symbol: ["std::ostringstream", "public", "<sstream>", "public"] },
-# Needed for unknown reasons
-{ include: ['<__algorithm/equal.h>', "private", '<algorithm>', "public"] },
-{ include: ['<__algorithm/unique.h>', "private", '<algorithm>', "public"] },
-{ include: ['<__type_traits/remove_reference.h>', "private", '<type_traits>', "public"] },
-{ include: ['<__functional/function.h>', "private", '<functional>', "public"] },
-{ include: ['<__utility/pair.h>', "private", '<utility>', "public"] },
+
+{ ref: "../../buildtools/third_party/libc++/trunk/include/libcxx.imp" },
 ]