m4: fix bootstrap on host with texinfo installed

texinfo is defaulted to UTF-8 now, but m4.texi is written in ISO-8859-1.
While we're at it, xlintify.

srcpkgs/m4/template

@@ -1,18 +1,24 @@
 # Template file for 'm4'
 pkgname=m4
 version=1.4.18
-revision=2
-patch_args="-Np1"
+revision=3
 bootstrap=yes
-replaces="chroot-m4>=0"
 build_style=gnu-configure
 configure_args="--enable-changeword --enable-threads"
 short_desc="GNU version of UNIX m4 macro language processor"
-homepage="https://www.gnu.org/software/m4/"
-license="GPL-3.0-or-later"
 maintainer="Enno Boland <gottox@voidlinux.org>"
+license="GPL-3.0-or-later"
+homepage="https://www.gnu.org/software/m4/"
 distfiles="${GNU_SITE}/${pkgname}/${pkgname}-${version}.tar.xz"
 checksum=f2c1e86ca0a404ff281631bdc8377638992744b175afb806e25871a24a934e07
+replaces="chroot-m4>=0"
+patch_args="-Np1"
+
+post_patch() {
+	# If texinfo was installed in host system,
+	# bootstrap is falling
+	vsed -i '1i @documentencoding ISO-8859-1' doc/m4.texi
+}
 
 pre_check() {
 	case "$XBPS_TARGET_MACHINE" in