platform requirements: Add attributes to die() function

Add both format string and ((noreturn)) attributes to the version of die()
used in the test programs in doc/platform-requirements.  As well as
potentially catching problems in format strings, this means that the
compiler and static checkers can properly reason about the fact that it
will exit, preventing bogus warnings.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

doc/platform-requirements/common.h

@@ -15,6 +15,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+__attribute__((format(printf, 1, 2), noreturn))
 static inline void die(const char *fmt, ...)
 {
 	va_list ap;