[PATCH-for-8.0] qemu/osdep.h: Do not declare function prototypes using extern keyword

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

By default, C function prototypes declared in headers are visible,
so there is no need to declare them as 'extern' functions. Remove
this redundancy. This also fixes when building under MSYS2:

  C:/msys64/mingw64/include/glib-2.0/glib/gmacros.h:1075:21: error: standard attributes in middle of decl-specifiers
  1075 | # define G_NORETURN [[noreturn]]
        |                     ^
  C:/msys64/code/qemu/src/include/qemu/osdep.h:240:8: note: in expansion of macro 'G_NORETURN'
  240 | extern G_NORETURN
        |        ^~~~~~~~~~

Reported-by: Simon Wörner <contact@simon-woerner.de>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1541
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/qemu/osdep.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index f68b5d8708..79c26c748a 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -237,7 +237,7 @@ extern "C" {
  * supports QEMU_ERROR, this will be reported at compile time; otherwise
  * this will be reported at link time due to the missing symbol.
  */
-extern G_NORETURN
+G_NORETURN
 void QEMU_ERROR("code path is reachable")
     qemu_build_not_reached_always(void);
 #if defined(__OPTIMIZE__) && !defined(__NO_INLINE__)
-- 
2.38.1