flycheck-pkg-config provides a convenient way for configuring
flycheck to use C library headers.
It configures flycheck-clang-include-path,
flycheck-gcc-include-path and flycheck-cppcheck-include-path
interactively.
You can install flycheck-pkg-config from
MELPA. M-x list-packages, navigate to
flycheck-pkg-config, then press i x.
M-x flycheck-pkg-config
