zephyr: printk: Use proper type for c_char

Rust 1.85 changes the type of `c_char` in `core::ffi` to better match
C.  This causes our explicit cast when calling `k_str_out` to break on
some platforms.  Fix this by casting to `c_char` which should always
match the type.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

zephyr/src/printk.rs

@@ -5,7 +5,7 @@
 //!
 //! This uses the `k_str_out` syscall, which is part of printk to output to the console.
 
-use core::fmt::{write, Arguments, Result, Write};
+use core::{ffi::c_char, fmt::{write, Arguments, Result, Write}};
 
 /// Print to Zephyr's console, without a newline.
 ///
@@ -92,7 +92,7 @@ impl Context {
     fn flush(&mut self) {
         if self.count > 0 {
             unsafe {
-                zephyr_sys::k_str_out(self.buf.as_mut_ptr() as *mut i8, self.count);
+                zephyr_sys::k_str_out(self.buf.as_mut_ptr() as *mut c_char, self.count);
             }
             self.count = 0;
         }