xbps-src: install_pkg: we know exact PATH for chroot case, use it.

xbps-src/shutils/pkgtarget_funcs.sh.in

@@ -129,14 +129,19 @@ install_pkg()
 		fi
 	fi
 
+	if [ -n "$IN_CHROOT" ]; then
+		DOINST_HELPER=/usr/local/libexec/doinst-helper
+	else
+		DOINST_HELPER=@@XBPS_INSTALL_LIBEXECDIR@@/doinst-helper
+	fi
+
 	# Install pkg into destdir.
 	env XBPS_MACHINE=${XBPS_MACHINE} wrksrc=${wrksrc}	\
 		MASTERDIR="${XBPS_MASTERDIR}"			\
 		BOOTSTRAP_PKG_REBUILD=$BOOTSTRAP_PKG_REBUILD	\
 		CONFIG_FILE=${XBPS_CONFIG_FILE}			\
 		${FAKEROOT_CMD} ${FAKEROOT_CMD_ARGS}		\
-		@@XBPS_INSTALL_LIBEXECDIR@@/doinst-helper	\
-		${curpkgn} || return $?
+		${DOINST_HELPER} ${curpkgn} || return $?
 
 	# Strip binaries/libraries.
 	strip_files