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

Created by: dbermond

When installing with the -I option a package which in turn has a dependency with multiple providers, makechrootpkg enters in 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.

There are other ways to fix it, like piping while :; do printf "y\n1\n"; done instead of yes y, but simply using --noconfirm looks simpler and better.

Example package to reproduce: flutter^AUR (depends on android-sdk^AUR). When executing extra-x86_64-build -- -I /path/to/android-sdk-26.1.1-1-x86_64.pkg.tar.zst, it will enter in an infinite loop because java-environment (dependency of android-sdk^AUR that is being installed with -I) has multiple providers.