[build] Fix a problem with win+gcc (mingw, msys, cygwin) causing some…

… optimized functions to segfault

configure.ac

@@ -137,6 +137,13 @@ AS_CASE([$host_os],
         ],
         [cygwin*|msys*|mingw*], [
          CFLAGS="$CFLAGS -D__USE_MINGW_ANSI_STDIO=1"
+         # Fix a bug in mingw gcc where stack doesn't get aligned properly, force all AVX instructions to be unaligned
+         if test x"${CC}" = x"gcc" ; then
+             AX_CHECK_COMPILE_FLAG([-Wa,-muse-unaligned-vector-move],
+                 [CFLAGS="-Wa,-muse-unaligned-vector-move $CFLAGS"],
+                 [AC_MSG_ERROR([-Wa,-muse-unaligned-vector-move not supported, required with mingw+gcc to fix alignment bugs, update the used gcc])]
+             )
+         fi
          AS_IF(
                [test "x$BITS" = "x32"], [
                 ASFLAGS="$ASFLAGS -fwin32 -DPREFIX -DHAVE_ALIGNED_STACK=0"
@@ -174,7 +181,7 @@ AS_IF([test "x$YASM" != "xno"], [have_yasm="yes"])
 AC_ARG_ENABLE([asm], [AS_HELP_STRING([--disable-asm], [disable assembly [no]])],
               [], [enable_asm="yes"]
 )
-AS_IF([test "x$enable_asm" != "xno" -a $have_yasm != "yes"],
+AS_IF([test "x$enable_asm" != "xno" -a "$have_yasm" != "yes"],
       [enable_asm="no"]
 )