fcntl: open should use a va_list

The current implementation of open requires the user to pass all three
args to the function. It should use a va_list and allow a user to
provide only the filename and flags.

src/fcntl/cbindgen.toml

@@ -1,5 +1,6 @@
-sys_includes = ["sys/types.h"]
+sys_includes = ["stdarg.h", "sys/types.h"]
 include_guard = "_FCNTL_H"
+trailer = "#include <bits/fcntl.h>"
 language = "C"
 
 [enum]

src/fcntl/src/lib.rs

@@ -33,7 +33,7 @@ pub const F_UNLCK: c_int = 2;
 
 #[no_mangle]
 pub extern "C" fn creat(path: *const c_char, mode: mode_t) -> c_int {
-    open(path, O_WRONLY | O_CREAT | O_TRUNC, mode)
+    sys_open(path, O_WRONLY | O_CREAT | O_TRUNC, mode)
 }
 
 #[no_mangle]
@@ -42,7 +42,7 @@ pub extern "C" fn fcntl(fildes: c_int, cmd: c_int, arg: c_int) -> c_int {
 }
 
 #[no_mangle]
-pub extern "C" fn open(path: *const c_char, oflag: c_int, mode: mode_t) -> c_int {
+pub extern "C" fn sys_open(path: *const c_char, oflag: c_int, mode: mode_t) -> c_int {
     platform::open(path, oflag, mode)
 }