ci(release): attach source archives to release and use them for AUR package

Gitea's /archive/ endpoint is disabled, which broke the AUR source download.
Build source tar.gz/zip with git archive, upload as release assets, and point
the PKGBUILD and checksum step at the release asset.

linux/arch/PKGBUILD

@@ -7,11 +7,11 @@ arch=('x86_64' 'aarch64')
 url="https://git.warky.dev/wdevs/relspecgo"
 license=('MIT')
 makedepends=('go')
-source=("$pkgname-$pkgver.zip::$url/archive/v$pkgver.zip")
+source=("$pkgname-$pkgver.zip::$url/releases/download/v$pkgver/relspec-v$pkgver-source.zip")
 sha256sums=('SKIP')
 
 build() {
-    cd "relspecgo"
+    cd "$pkgname-$pkgver"
     export CGO_ENABLED=0
     go build \
         -trimpath \
@@ -20,12 +20,12 @@ build() {
 }
 
 check() {
-    cd "relspecgo"
+    cd "$pkgname-$pkgver"
     go test ./...
 }
 
 package() {
-    cd "relspecgo"
+    cd "$pkgname-$pkgver"
 
     # Binary
     install -Dm755 "$pkgname" "$pkgdir/usr/bin/$pkgname"