Make FileSystem.cake C-compatible

* Include stdbool
* Properly check features in preprocessor for selecting strerror_r
* Properly mark dirent as struct dirent

src/FileSystem.cake

@@ -4,7 +4,7 @@
         &with-decls "DynamicArray.cake")
 
 (c-import "<stdio.h>"
-          &with-decls "<stddef.h>") ;; for size_t
+          &with-decls "<stddef.h>" "<stdbool.h>") ;; for size_t
 
 (var filesystem-verbose-logging bool false)
 ;; (var filesystem-verbose-logging bool true)
@@ -107,9 +107,9 @@
 
   (defun-local set-error-string (error-string-buffer (addr char) error-string-buffer-length size_t)
     ;; See man strerror(3)
-    (if (and (>= _POSIX_C_SOURCE 200112L) (not _GNU_SOURCE))
-        ;; XSI-complient version always writes error string to buffer
-        (scope (var return-str (addr (const char))
+    (if-c-preprocessor (and (>= _POSIX_C_SOURCE 200112L) (not _GNU_SOURCE))
+        ;; XSI-compliant version always writes error string to buffer
+        (scope (var return-value int
                  (strerror_r errno error-string-buffer error-string-buffer-length)))
         ;; GNU version only writes to buffer sometimes; we need to copy to our buffer in that case
         (scope
@@ -140,7 +140,7 @@
       (set-error-string error-string-buffer error-string-buffer-length)
       (perror "read-directory")
       (return false))
-    (c-for (var entry (addr dirent) (readdir directory))
+    (c-for (var entry (addr (struct dirent)) (readdir directory))
         entry
         (set entry (readdir directory))
       (fsdebugf "%s" (path entry > d_name))
@@ -204,7 +204,7 @@
       (if (token-splice os-directory-variable)
           (scope
            (var (token-splice entry-full-path-variable) (array 2048 char) (array 0))
-           (c-for (var (token-splice os-entry-variable) (addr dirent)
+           (c-for (var (token-splice os-entry-variable) (addr (struct dirent))
                     (readdir (token-splice os-directory-variable)))
                (token-splice os-entry-variable)
                (set (token-splice os-entry-variable) (readdir (token-splice os-directory-variable)))
@@ -266,7 +266,7 @@
       (perror "read-directory")
       (return false))
     (defer (closedir directory))
-    (c-for (var entry (addr dirent) (readdir directory))
+    (c-for (var entry (addr (struct dirent)) (readdir directory))
         entry
         (set entry (readdir directory))
       (fsdebugf "%s" (path entry > d_name))