Fix for gcc being a dummy

Also clang being too permissive

- gcc apparently can't cope with linker args coming before the file
  name, that causes a bunch of "undefined reference" errors, whereas
  clang is perfectly happy with it
- on the other hand clang apparently exposes unexpected symbols
  without needing to include the corresponding header, so add those

regex-filtered/re2/Makefile

@@ -4,7 +4,7 @@ LDFLAGS += -lre2
 .PHONY: clean
 
 bench: bench.cpp
-	$(CXX) $(CXXFLAGS) $(LDFLAGS) $^ -o $@
+	$(CXX) $(CXXFLAGS) $^ -o $@ $(LDFLAGS)
 
 clean:
 	@rm bench

regex-filtered/re2/bench.cpp

@@ -1,5 +1,7 @@
+#include <cassert>
 #include <chrono>
 #include <fstream>
+#include <iomanip>
 #include <iostream>
 #include <re2/filtered_re2.h>
 #include <re2/re2.h>