osdep: Remove local definition of macro offsetof

The macro offsetof is defined in stddef.h. It is conforming to
the standards C89, C99 and POSIX.1-2001 (see man page), so it
is a sufficiently old standard.

Therefore chances are very high that QEMU never needs a local
definition of this macro.

osdep.h already includes stddef.h, so this patch simply removes
the unneeded code from the files configure and osdep.h.

If we ever need the local definition again, it should be added
to compiler.h (the macro is usually provided with the compiler,
it is not OS specific).

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

configure

@@ -2524,17 +2524,6 @@ if test "$darwin" != "yes" -a "$mingw32" != "yes" -a "$solaris" != yes -a \
 fi
 
 ##########################################
-# check if the compiler defines offsetof
-
-need_offsetof=yes
-cat > $TMPC << EOF
-#include <stddef.h>
-int main(void) { struct s { int f; }; return offsetof(struct s, f); }
-EOF
-if compile_prog "" "" ; then
-    need_offsetof=no
-fi
-
 # spice probe
 if test "$spice" != "no" ; then
   cat > $TMPC << EOF
@@ -3199,9 +3188,6 @@ fi
 if test "$tcg_interpreter" = "yes" ; then
   echo "CONFIG_TCG_INTERPRETER=y" >> $config_host_mak
 fi
-if test "$need_offsetof" = "yes" ; then
-  echo "CONFIG_NEED_OFFSETOF=y" >> $config_host_mak
-fi
 if test "$fdatasync" = "yes" ; then
   echo "CONFIG_FDATASYNC=y" >> $config_host_mak
 fi

osdep.h

@@ -26,9 +26,6 @@
 #define unlikely(x)   __builtin_expect(!!(x), 0)
 #endif
 
-#ifdef CONFIG_NEED_OFFSETOF
-#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *) 0)->MEMBER)
-#endif
 #ifndef container_of
 #define container_of(ptr, type, member) ({                      \
         const typeof(((type *) 0)->member) *__mptr = (ptr);     \