clang-tidy: Disable performance-avoid-endl check

See: https://clang.llvm.org/extra/clang-tidy/checks/performance/avoid-endl.html

Author: hebasto

.clang-tidy

@@ -20,6 +20,7 @@ modernize-*,
 -modernize-use-trailing-return-type,
 -modernize-use-using,
 performance-*,
+-performance-avoid-endl,
 -performance-noexcept-move-constructor,
 readability-*,
 -readability-braces-around-statements,