ci: fix arch package build directory structure

- Create proper source directory structure for makepkg
- Add -p flag to runuser to preserve env vars
- Add root group to nobody user for proper permissions
- Restore directory changes in PKGBUILD

.github/workflows/release.yml

@@ -189,12 +189,15 @@ jobs:
         run: |
           VERSION=$(grep -m1 'version =' Cargo.toml | cut -d '"' -f2)
           sed -i "s/pkgver=.*/pkgver=$VERSION/" dist/arch/PKGBUILD
-          cp dist/arch/PKGBUILD .
+          mkdir -p /tmp/pkg/src
+          cp -r . /tmp/pkg/src/modbus-relay
+          cp dist/arch/PKGBUILD /tmp/pkg
 
       - name: Build package
         run: |
+          cd /tmp/pkg
           chown -R nobody:nobody .
-          runuser -u nobody -- makepkg -s --noconfirm
+          runuser -p -u nobody -g root -- makepkg -s --noconfirm
 
       - name: Upload artifacts
         uses: actions/upload-artifact@v4

dist/arch/PKGBUILD

@@ -11,10 +11,13 @@ makedepends=('cargo' 'git')
 backup=('etc/modbus-relay/config.yaml')
 
 build() {
+  cd "$srcdir/$pkgname"
   cargo build --release
 }
 
 package() {
+  cd "$srcdir/$pkgname"
+
   # Binary
   install -Dm755 "target/release/$pkgname" "$pkgdir/usr/bin/$pkgname"