Avoid "undefined reference to `memset'" error when building with
USE=custom-cflags and -O3 in CFLAGS with gcc-4.8.

See:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888
http://bugs.winehq.org/show_bug.cgi?id=33521
https://bugs.gentoo.org/show_bug.cgi?id=480508
https://bugs.gentoo.org/717026

diff -pruN a/configure.ac b/configure.ac
--- a/configure.ac	2020-04-11 11:23:35.000000000 +0200
+++ b/configure.ac	2020-04-11 11:31:41.118882980 +0200
@@ -2098,6 +2098,7 @@ then
   WINE_TRY_CFLAGS([-Werror=unknown-warning-option],[CFLAGS="$CFLAGS -Werror=unknown-warning-option"])
   WINE_TRY_CFLAGS([-Werror=unused-command-line-argument],[CFLAGS="$CFLAGS -Werror=unused-command-line-argument"])
   WINE_TRY_CFLAGS([-Werror=ignored-optimization-argument],[CFLAGS="$CFLAGS -Werror=ignored-optimization-argument"])
+  WINE_TRY_CFLAGS([-fno-tree-loop-distribute-patterns])
   WINE_TRY_CFLAGS([-fcf-protection=none])
   WINE_TRY_CFLAGS([-fno-stack-protector])
   WINE_TRY_CFLAGS([-fno-strict-aliasing])