makechrootpkg: fix an infinite loop when installing package with -I

When installing with the '-I' option a package which in turn has
a dependency with multiple providers, makechrootpkg enters an
infinite loop. This happens because we are using the 'pacman -U'
command piped with 'yes y'. The 'yes y' command outputs only 'y'
lines, but when installing a dependency package with multiple
providers pacman expects a number as the input. Being such,
makechrootpkg outputs this endlessly:

    Enter a number (default=1): error: invalid number: y

Using the pacman '--noconfirm' option without piping 'yes y' fixes
the issue.

makechrootpkg.in

@@ -145,7 +145,7 @@ install_packages() {
 
 	cp -- "${install_pkgs[@]}" "$copydir/root/"
 	arch-nspawn "$copydir" "${bindmounts_ro[@]}" "${bindmounts_rw[@]}" \
-		bash -c 'yes y | pacman -U -- "$@"' -bash "${pkgnames[@]/#//root/}"
+		bash -c 'pacman -U --noconfirm -- "$@"' -bash "${pkgnames[@]/#//root/}"
 	ret=$?
 	rm -- "${pkgnames[@]/#/$copydir/root/}"