Revert "bison: update to 3.7."

This reverts commit fe1cae9869.

See: https://www.openwall.com/lists/musl/2020/07/30/3

srcpkgs/bison/template

@@ -1,7 +1,8 @@
 # Template file for 'bison'
 pkgname=bison
-version=3.7
-revision=1
+reverts="3.7_1"
+version=3.6.4
+revision=2
 build_style=gnu-configure
 hostmakedepends="help2man perl m4"
 depends="m4"
@@ -11,7 +12,7 @@ maintainer="Enno Boland <gottox@voidlinux.org>"
 license="GPL-3.0-or-later"
 homepage="http://www.gnu.org/software/bison/bison.html"
 distfiles="${GNU_SITE}/bison/bison-${version}.tar.xz"
-checksum=07b25fbf4de2f2c686e8bff50fdb69efda49b6f9f7377dad1884f9508a28592b
+checksum=8b13473b31ca7fcf65e5e8a74224368ffd5df19275602a9c9567ba393f18577d
 alternatives="
  yacc:yacc:/usr/bin/bison-yacc
  yacc:yacc.1:/usr/share/man/man1/bison-yacc.1"