Include pkgrel in the local source filename

Artifact rebuilds (e.g. dependency bundling) change the file behind
<pkg>-<ver>.tar.zst while keeping its name, so users with the previous
file in their AUR helper cache hit a checksum mismatch. Naming the local
download <pkg>-<ver>-<rel>.tar.zst makes every rebuild a fresh file.

waydroid-helper-bin/PKGBUILD

@@ -17,7 +17,7 @@ optdepends=('bindfs: shared folders support'
             'waydroid: the container this tool configures')
 provides=('waydroid-helper')
 conflicts=('waydroid-helper')
-source=("https://github.com/Felitendo/PKGBUILDS/releases/download/${pkgname}-${pkgver}/${pkgname}-${pkgver}.tar.zst")
+source=("${pkgname}-${pkgver}-${pkgrel}.tar.zst::https://github.com/Felitendo/PKGBUILDS/releases/download/${pkgname}-${pkgver}/${pkgname}-${pkgver}.tar.zst")
 sha256sums=('8a02695c6a3f102d1fa2a0b6266bb1978874338eac5a33b3391ada3243c01e56')
 
 package() {