How to run autoconf on gcc/configure.ac ?

[Georg-Johann Lay <avr@xxxxxxxx>]

Using autoconf2.69 on gcc/configure.ac from master, I have the
following issue:

There are unexpected changes in the generated configure that are like

diff --git a/gcc/configure b/gcc/configure
index de72cb1e1fe..1bd6f493e53 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -6229,7 +6229,7 @@ else
     We can't simply define LARGE_OFF_T to be 9223372036854775807,
     since some C++ compilers masquerading as C compilers
     incorrectly reject 9223372036854775807.  */
-#define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
+#define LARGE_OFF_T ((((off_t) 1 << 31) << 31) - 1 + (((off_t) 1 << 31) << 31))
   int off_t_is_large[(LARGE_OFF_T % 2147483629 == 721
                       && LARGE_OFF_T % 2147483647 == 1)
                      ? 1 : -1];
@@ -6275,7 +6275,7 @@ else
     We can't simply define LARGE_OFF_T to be 9223372036854775807,
     since some C++ compilers masquerading as C compilers
     incorrectly reject 9223372036854775807.  */
-#define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
+#define LARGE_OFF_T ((((off_t) 1 << 31) << 31) - 1 + (((off_t) 1 << 31) << 31))
   int off_t_is_large[(LARGE_OFF_T % 2147483629 == 721
                       && LARGE_OFF_T % 2147483647 == 1)
                      ? 1 : -1];

etc. and I don't know how to avoid them.

Using:

configure2.69
automake-1.15.1
aclocal_1.15.1

Thanks in advance,

Johann