(c-add-style "cts"
             '("gnu"
               (c-offsets-alist . ((substatement-open . 0)))
               (c-basic-offset . 4)))

(defconst cts-c-regexp
  (concat "/c/\\(VK-GL-CTS\\|Vulkan-LoaderAndValidationLayers\\)/.*\\(?:c\\|cc\\|h\\|cpp\\|hpp\\)\\'"))

(defun maybe-set-cts-c-style ()
  (when (and (buffer-file-name)
             (string-match cts-c-regexp (buffer-file-name)))
    (c-set-style "cts")
    (setq tab-width 4)
    (setq indent-tabs-mode t)))

(add-hook 'c-mode-hook 'maybe-set-cts-c-style)
(add-hook 'c++-mode-hook 'maybe-set-cts-c-style)