fix(main/xmlto): Don't hardcode build-machine paths to tools

Now it actually works on my phone

packages/xmlto/build.sh

@@ -3,12 +3,25 @@ TERMUX_PKG_DESCRIPTION="Convert xml to many other formats"
 TERMUX_PKG_LICENSE="GPL-2.0"
 TERMUX_PKG_MAINTAINER="@termux"
 TERMUX_PKG_VERSION="0.0.29"
+TERMUX_PKG_REVISION="1"
 TERMUX_PKG_SRCURL=https://www.pagure.io/xmlto/archive/${TERMUX_PKG_VERSION}/xmlto-${TERMUX_PKG_VERSION}.tar.gz
 TERMUX_PKG_SHA256=40504db68718385a4eaa9154a28f59e51e59d006d1aa14f5bc9d6fded1d6017a
 TERMUX_PKG_DEPENDS="xsltproc"
 TERMUX_PKG_AUTO_UPDATE=true
 TERMUX_PKG_UPDATE_METHOD=repology
 
+# XMLTO_BASH_PATH needs to be absolute. The massage step fixes it.
+TERMUX_PKG_EXTRA_CONFIGURE_ARGS="XMLTO_BASH_PATH=/bin/bash MKTEMP=mktemp FIND=find GETOPT=getopt PAPER_CONF=paperconf LOCALE=locale XMLLINT=xmllint XSLTPROC=xsltproc DBLATEX=dblatex FOP=fop XMLTEX=xmltex PDFXMLTEX=pdfxmltex LYNX=lynx LINKS=elinks W3M=w3m TAIL=tail GREP=grep SED=sed CP=cp ZIP=zip"
+
 termux_step_pre_configure() {
+	# AC_PATH_PROG insists on using an absolute path found on the
+	# build system, which would be fine if they were just for
+	# building, but lots of them end up in the installed "xmlto"
+	# script, which is bad when cross-compiling.
+	#
+	# AC_CHECK_PROG lets us choose the exact spelling, at least
+	# when preceded by a matching AC_ARG_VAR - and xmlto's
+	# configure.ac very carefully does this before each AC_*_PROG.
+	sed -e 's/^AC_PATH_PROG/AC_CHECK_PROG/' -i~ configure.ac
 	autoreconf -fi
 }