Add configure check for 32 bit build support on arm64-linux.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14373 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/configure.ac b/configure.ac
index fa6a020..c2eaac2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -397,7 +397,7 @@
 # does not support building 32 bit programs
 
 case "$ARCH_MAX-$VGCONF_OS" in
-     amd64-linux|ppc64be-linux)
+     amd64-linux|ppc64be-linux|arm64-linux)
         AC_MSG_CHECKING([for 32 bit build support])
         safe_CFLAGS=$CFLAGS
         CFLAGS="-m32"