Steps to Reproduce:

1. Build the following package and install with `pacman -U`.

pkgname=symlink-test
pkgver=1.0
pkgrel=1
backup=("etc/symlink-test")
arch=('any')

package() {
install -d -m 0755 "${pkgdir}/etc"
ln -sf first-target "${pkgdir}/etc/symlink-test"
}

2. Replace the installed symlink by a regular file.

# rm /etc/symlink-test && echo test > /etc/symlink-test

3. Reinstall the above package with `pacman -U`. Observe that this operation completes successfully.
4. Update the above package to a newer version that installs the same symlink with a different target, and install with `pacman -U`. Observe that pacman hangs at "upgrading symlink-test" and cannot be terminated by SIGINT.