Add test for fixed args count

tests/fail-dep/libc/wrong_fixed_arg_count.rs

@@ -0,0 +1,14 @@
+//@ignore-target: windows # File handling is not implemented yet
+//@compile-flags: -Zmiri-disable-isolation
+use std::ffi::{CString, OsStr};
+use std::os::unix::ffi::OsStrExt;
+
+extern "C" {
+    fn open(path: *const libc::c_char, ...) -> libc::c_int;
+}
+
+fn main() {
+    let c_path = CString::new(OsStr::new("./text").as_bytes()).expect("CString::new failed");
+    let _fd = unsafe { open(c_path.as_ptr(), libc::O_RDWR) };
+    //~^ ERROR: incorrect number of fixed args
+}

tests/fail-dep/libc/wrong_fixed_arg_count.stderr

@@ -0,0 +1,15 @@
+error: Undefined Behavior: incorrect number of fixed args for `open/open64`: got 1, expected 2
+  --> tests/fail-dep/libc/wrong_fixed_arg_count.rs:LL:CC
+   |
+LL |     let _fd = unsafe { open(c_path.as_ptr(), libc::O_RDWR) };
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ incorrect number of fixed args for `open/open64`: got 1, expected 2
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE:
+   = note: inside `main` at tests/fail-dep/libc/wrong_fixed_arg_count.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+