Buildroot specific
  diff -ru rpm-5.1.9_vanilla/xz/configure rpm-5.1.9_short-circuit-c99/xz/configure
  --- rpm-5.1.9_vanilla/xz/configure	2009-04-18 16:47:23.000000000 +0000
  +++ rpm-5.1.9_short-circuit-c99/xz/configure	2009-08-04 08:25:59.000000000 +0000
  @@ -4970,214 +4970,7 @@
     am__fastdepCC_FALSE=
   fi
   
  -
  -   { $as_echo "$as_me:$LINENO: checking for $CC option to accept ISO C99" >&5
  -$as_echo_n "checking for $CC option to accept ISO C99... " >&6; }
  -if test "${ac_cv_prog_cc_c99+set}" = set; then
  -  $as_echo_n "(cached) " >&6
  -else
  -  ac_cv_prog_cc_c99=no
  -ac_save_CC=$CC
  -cat >conftest.$ac_ext <<_ACEOF
  -/* confdefs.h.  */
  -_ACEOF
  -cat confdefs.h >>conftest.$ac_ext
  -cat >>conftest.$ac_ext <<_ACEOF
  -/* end confdefs.h.  */
  -#include <stdarg.h>
  -#include <stdbool.h>
  -#include <stdlib.h>
  -#include <wchar.h>
  -#include <stdio.h>
  -
  -// Check varargs macros.  These examples are taken from C99 6.10.3.5.
  -#define debug(...) fprintf (stderr, __VA_ARGS__)
  -#define showlist(...) puts (#__VA_ARGS__)
  -#define report(test,...) ((test) ? puts (#test) : printf (__VA_ARGS__))
  -static void
  -test_varargs_macros (void)
  -{
  -  int x = 1234;
  -  int y = 5678;
  -  debug ("Flag");
  -  debug ("X = %d
  ", x);
  -  showlist (The first, second, and third items.);
  -  report (x>y, "x is %d but y is %d", x, y);
  -}
  -
  -// Check long long types.
  -#define BIG64 18446744073709551615ull
  -#define BIG32 4294967295ul
  -#define BIG_OK (BIG64 / BIG32 == 4294967297ull && BIG64 % BIG32 == 0)
  -#if !BIG_OK
  -  your preprocessor is broken;
  -#endif
  -#if BIG_OK
  -#else
  -  your preprocessor is broken;
  -#endif
  -static long long int bignum = -9223372036854775807LL;
  -static unsigned long long int ubignum = BIG64;
  -
  -struct incomplete_array
  -{
  -  int datasize;
  -  double data[];
  -};
  -
  -struct named_init {
  -  int number;
  -  const wchar_t *name;
  -  double average;
  -};
  -
  -typedef const char *ccp;
  -
  -static inline int
  -test_restrict (ccp restrict text)
  -{
  -  // See if C++-style comments work.
  -  // Iterate through items via the restricted pointer.
  -  // Also check for declarations in for loops.
  -  for (unsigned int i = 0; *(text+i) != '\0'; ++i)
  -    continue;
  -  return 0;
  -}
  -
  -// Check varargs and va_copy.
  -static void
  -test_varargs (const char *format, ...)
  -{
  -  va_list args;
  -  va_start (args, format);
  -  va_list args_copy;
  -  va_copy (args_copy, args);
  -
  -  const char *str;
  -  int number;
  -  float fnumber;
  -
  -  while (*format)
  -    {
  -      switch (*format++)
  -	{
  -	case 's': // string
  -	  str = va_arg (args_copy, const char *);
  -	  break;
  -	case 'd': // int
  -	  number = va_arg (args_copy, int);
  -	  break;
  -	case 'f': // float
  -	  fnumber = va_arg (args_copy, double);
  -	  break;
  -	default:
  -	  break;
  -	}
  -    }
  -  va_end (args_copy);
  -  va_end (args);
  -}
  -
  -int
  -main ()
  -{
  -
  -  // Check bool.
  -  _Bool success = false;
  -
  -  // Check restrict.
  -  if (test_restrict ("String literal") == 0)
  -    success = true;
  -  char *restrict newvar = "Another string";
  -
  -  // Check varargs.
  -  test_varargs ("s, d' f .", "string", 65, 34.234);
  -  test_varargs_macros ();
  -
  -  // Check flexible array members.
  -  struct incomplete_array *ia =
  -    malloc (sizeof (struct incomplete_array) + (sizeof (double) * 10));
  -  ia->datasize = 10;
  -  for (int i = 0; i < ia->datasize; ++i)
  -    ia->data[i] = i * 1.234;
  -
  -  // Check named initializers.
  -  struct named_init ni = {
  -    .number = 34,
  -    .name = L"Test wide string",
  -    .average = 543.34343,
  -  };
  -
  -  ni.number = 58;
  -
  -  int dynamic_array[ni.number];
  -  dynamic_array[ni.number - 1] = 543;
  -
  -  // work around unused variable warnings
  -  return (!success || bignum == 0LL || ubignum == 0uLL || newvar[0] == 'x'
  -	  || dynamic_array[ni.number - 1] != 543);
  -
  -  ;
  -  return 0;
  -}
  -_ACEOF
  -for ac_arg in '' -std=gnu99 -std=c99 -c99 -AC99 -xc99=all -qlanglvl=extc99
  -do
  -  CC="$ac_save_CC $ac_arg"
  -  rm -f conftest.$ac_objext
  -if { (ac_try="$ac_compile"
  -case "(($ac_try" in
  -  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
  -  *) ac_try_echo=$ac_try;;
  -esac
  -eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
  -$as_echo "$ac_try_echo") >&5
  -  (eval "$ac_compile") 2>conftest.er1
  -  ac_status=$?
  -  grep -v '^ *+' conftest.er1 >conftest.err
  -  rm -f conftest.er1
  -  cat conftest.err >&5
  -  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
  -  (exit $ac_status); } && {
  -	 test -z "$ac_c_werror_flag" ||
  -	 test ! -s conftest.err
  -       } && test -s conftest.$ac_objext; then
  -  ac_cv_prog_cc_c99=$ac_arg
  -else
  -  $as_echo "$as_me: failed program was:" >&5
  -sed 's/^/| /' conftest.$ac_ext >&5
  -
  -
  -fi
  -
  -rm -f core conftest.err conftest.$ac_objext
  -  test "x$ac_cv_prog_cc_c99" != "xno" && break
  -done
  -rm -f conftest.$ac_ext
  -CC=$ac_save_CC
  -
  -fi
  -# AC_CACHE_VAL
  -case "x$ac_cv_prog_cc_c99" in
  -  x)
  -    { $as_echo "$as_me:$LINENO: result: none needed" >&5
  -$as_echo "none needed" >&6; } ;;
  -  xno)
  -    { $as_echo "$as_me:$LINENO: result: unsupported" >&5
  -$as_echo "unsupported" >&6; } ;;
  -  *)
  -    CC="$CC $ac_cv_prog_cc_c99"
  -    { $as_echo "$as_me:$LINENO: result: $ac_cv_prog_cc_c99" >&5
  -$as_echo "$ac_cv_prog_cc_c99" >&6; } ;;
  -esac
  -
  -
  -
  -if test x$ac_cv_prog_cc_c99 = xno ; then
  -	{ { $as_echo "$as_me:$LINENO: error: No C99 compiler was found." >&5
  -$as_echo "$as_me: error: No C99 compiler was found." >&2;}
  -   { (exit 1); exit 1; }; }
  -fi
  +CC="$CC -std=c99"
   
   if test "x$CC" != xcc; then
     { $as_echo "$as_me:$LINENO: checking whether $CC and cc understand -c and -o together" >&5
  diff -ru rpm-5.1.9_vanilla/xz/configure.ac rpm-5.1.9_short-circuit-c99/xz/configure.ac
  --- rpm-5.1.9_vanilla/xz/configure.ac	2009-02-16 17:07:46.000000000 +0000
  +++ rpm-5.1.9_short-circuit-c99/xz/configure.ac	2009-08-04 08:25:28.000000000 +0000
  @@ -402,10 +402,7 @@
   AM_INIT_AUTOMAKE([1.10 foreign tar-v7 filename-length-max=99])
   AC_PROG_LN_S
   
  -AC_PROG_CC_C99
  -if test x$ac_cv_prog_cc_c99 = xno ; then
  -	AC_MSG_ERROR([No C99 compiler was found.])
  -fi
  +CC="$CC -std=c99"
   
   AM_PROG_CC_C_O
   AM_PROG_AS