Update SDL2 to the latest commit (85bbf8e)

libs/SDL2/autogen.sh

@@ -1,5 +1,7 @@
 #!/bin/sh
 
+set -e
+
 echo "Generating build information using autoconf"
 echo "This may take a while ..."
 
@@ -10,11 +12,7 @@ cd "$srcdir"
 # Regenerate configuration files
 cat acinclude/* >aclocal.m4
 
-if test "$AUTOCONF"x = x; then
-  AUTOCONF=autoconf
-fi
-
-$AUTOCONF || exit 1
+"${AUTOCONF:-autoconf}"
 rm aclocal.m4
 rm -rf autom4te.cache