Make configure remove the ares_build.h file included in distribution tarballs.

ares/configure.ac

@@ -60,6 +60,11 @@ if test -z "$AR" || test "$AR" = "not_found"; then
 fi
 AC_SUBST([AR])
 
+dnl Remove non-configure distributed ares_build.h
+if test -f ${srcdir}/ares_build.h; then
+  rm -f ${srcdir}/ares_build.h
+fi
+
 dnl Fetch c-ares version from ares_version.h
 VERSION=`$SED -ne 's/^#define ARES_VERSION_STR "\(.*\)"/\1/p' ${srcdir}/ares_version.h`
 AM_INIT_AUTOMAKE([c-ares], [$VERSION])