Drop C++11 support which is now not required since we've switched to use acutest unittest framework.

syoyo · syoyo · commit ed6824d0c1ac · 2019-06-20T13:46:41.000+09:00
diff --git a/tests/Makefile b/tests/Makefile
@@ -4,7 +4,7 @@ CXX = clang++
 CXXFLAGS ?= -g -O1
 
 tester: tester.cc ../tiny_obj_loader.h
-	$(CXX) $(CXXFLAGS) -std=c++11 -fsanitize=address -o tester tester.cc
+	$(CXX) $(CXXFLAGS) -fsanitize=address -o tester tester.cc
 
 all: tester
 
