Really add AM_PROG_CC_C_O this time, rather than AC_PROG_CC_C_O.

BUG: 92331


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@2888 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/configure.in b/configure.in
index 25beccb..516097a 100644
--- a/configure.in
+++ b/configure.in
@@ -11,7 +11,7 @@
 
 AC_PROG_LN_S
 AC_PROG_CC
-AC_PROG_CC_C_O
+AM_PROG_CC_C_O
 AC_PROG_CPP
 AC_PROG_CXX
 AC_PROG_RANLIB