Do not peerdir contrib/libs/cxxsupp/libcxxrt from _LINK_UNIT()

All the logic regarding C++ runtime selection lays in contrib/libs/cxxsupp/libcxx/ya.make and we better keep it this way for now.
commit_hash:f87a620355a344b52195d9e734cd9f5b3099433b

build/ymake.core.conf

@@ -1084,10 +1084,6 @@ module _LINK_UNIT: _BASE_UNIT {
         PEERDIR+=contrib/libs/clang${CLANG_VER}-rt/lib/profile
     }
 
-    when ($USE_LIBCXXRT == "yes") {
-        PEERDIR += contrib/libs/cxxsupp/libcxxrt
-    }
-
     when ($USE_DYNAMIC_CUDA == "yes") {
         LINK_DYN_LIB_FLAGS += --dynamic-cuda
         LINK_SCRIPT_EXE_FLAGS += --dynamic-cuda