xbps-src: infrastructure changes required for "nonfree" keyword in tmpls.

- The chroot target now execs masterdir/bin/xbps-shell to set up correct envvars.
- 2 pkgs are now in nonfree repo: adobe-flash-plugin and jre.
- Renamed some vars in xbps-src to be in uppercase, notably XBPS_MACHINE.
- make-repoidx target now creates the index for all "known" directories specified
  via XBPS_PACKAGESDIR: XBPS_MACHINE, noarch, and nonfree/XBPS_MACHINE.

srcpkgs/binutils/template

@@ -42,7 +42,7 @@ do_build()
 
 do_install()
 {
-	if [ "$xbps_machine" = "x86_64" ]; then
+	if [ "$XBPS_MACHINE" = "x86_64" ]; then
 		mkdir -p ${SRCPKGDESTDIR}/usr/lib
 		cd ${SRCPKGDESTDIR}/usr && ln -s lib lib64 && cd ${wrksrc}
 	fi