This patch is a backport of the fix proposed at:
https://bugs.launchpad.net/ubuntu/+source/mksh/+bug/1058035

diff -urN mksh/Build.sh mksh.new/Build.sh
--- mksh/Build.sh	2012-12-11 14:28:56.632807230 +0100
+++ mksh.new/Build.sh	2012-12-11 14:35:23.704817141 +0100
@@ -1530,9 +1530,11 @@
 /* but the next three are; we REQUIRE signed integer wraparound */
 cta(ari_is_signed, (mksh_ari_t)-1 < (mksh_ari_t)0);
 cta(ari_has_31_bit, 0 < (mksh_ari_t)(((((mksh_ari_t)1 << 15) << 15) - 1) * 2 + 1));
+#if !defined(MKSH_GCC565048)
 cta(ari_sign_32_bit_and_wrap,
     (mksh_ari_t)(((((mksh_ari_t)1 << 15) << 15) - 1) * 2 + 1) >
     (mksh_ari_t)(((((mksh_ari_t)1 << 15) << 15) - 1) * 2 + 2));
+#endif
 /* the next assertion is probably not really needed */
 cta(uari_is_4_char, sizeof(mksh_uari_t) == 4);
 /* but the next four are; we REQUIRE unsigned integer wraparound */