clang-check does not find

I am trying to run Ale as my linter, which in turn uses clang-check to lint my code.

$ clang-check FeatureManager.h
Error while trying to load a compilation database:
Could not auto-detect compilation database for file "FeatureManager.h"
No compilation database found in /home/babbleshack/ or any parent directory
json-compilation-database: Error while opening JSON database: No such file or directory
Running without flags.
/home/babbleshack/FeatureManager.h:6:10: fatal error: 'unordered_map' file not found
#include <unordered_map>
         ^~~~~~~~~~~~~~~
1 error generated.
Error while processing /home/babbleshack/FeatureManager.h.

Whereas compiling with clang++ returns only a warning.

$ clang++ -std=c++11 -Wall FeatureManager.cxx FeatureManager.h
clang-5.0: warning: treating 'c-header' input as 'c++-header' when in C++ mode, this behavior is deprecated [-Wdeprecated]

There are no flags to clang-check allowing me to set compilation flags.