Mark LibC's assertion faillure helper with __NORETURN.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/9bd09454e3f

LibC/assert.cpp

@@ -4,11 +4,10 @@
 
 extern "C" {
 
-extern void __assertion_failed(const char* msg, const char* file, unsigned line, const char* func)
+void __assertion_failed(const char* msg, const char* file, unsigned line, const char* func)
 {
     fprintf(stderr, "ASSERTION FAILED: %s\n%s:%u in %s\n", msg, file, line, func);
     abort();
 }
 
 }
-

LibC/assert.h

@@ -4,7 +4,7 @@
 
 __BEGIN_DECLS
 
-void __assertion_failed(const char* msg, const char* file, unsigned line, const char* func);
+void __assertion_failed(const char* msg, const char* file, unsigned line, const char* func) __NORETURN;
 
 #define assert(expr) ((expr) ? (void)0 : __assertion_failed(#expr, __FILE__, __LINE__, __PRETTY_FUNCTION__))
 #define CRASH() do { asm volatile("ud2"); } while(0)

LibC/sys/cdefs.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #define ALWAYS_INLINE inline __attribute__ ((always_inline))
+#define __NORETURN __attribute__ ((noreturn))
 
 #ifdef __cplusplus
 #define __BEGIN_DECLS extern "C" {