fix(release): use %{_sourcedir} in RPM spec instead of absolute paths

rpmbuild runs %install from its own working directory where
 is undefined. Copy artifacts into SOURCES and use
rpmbuild's %{_sourcedir} macro to locate them.

scripts/release.sh

@@ -144,6 +144,7 @@ build_rpm() {
   mkdir -p "$buildroot/usr/local/bin"
   mkdir -p "$buildroot/usr/share/doc/$pkg_name"
 
+  # Copy binary and systemd unit into the buildroot
   cp "$BUILD_DIR/$binary" "$buildroot/usr/local/bin/$pkg_name"
   chmod 755 "$buildroot/usr/local/bin/$pkg_name"
 
@@ -154,6 +155,13 @@ build_rpm() {
 
   [[ -f "README.md" ]] && cp "README.md" "$buildroot/usr/share/doc/$pkg_name/"
 
+  # Also copy into SOURCES so rpmbuild %install can find them
+  cp "$BUILD_DIR/$binary" "$rpm_dir/SOURCES/$pkg_name"
+  if [[ -n "$systemd_unit" && -f "$systemd_unit" ]]; then
+    cp "$systemd_unit" "$rpm_dir/SOURCES/$(basename "$systemd_unit")"
+  fi
+  [[ -f "README.md" ]] && cp "README.md" "$rpm_dir/SOURCES/README.md"
+
   # File list
   local file_list
   file_list="%attr(755, root, root) /usr/local/bin/$pkg_name"
@@ -183,20 +191,20 @@ $description
 %install
 rm -rf %{buildroot}
 mkdir -p %{buildroot}/usr/local/bin
-cp $BUILD_DIR/$binary %{buildroot}/usr/local/bin/$pkg_name
+cp %{_sourcedir}/$pkg_name %{buildroot}/usr/local/bin/$pkg_name
 chmod 755 %{buildroot}/usr/local/bin/$pkg_name
 SPEC
 
   if [[ -n "$systemd_unit" && -f "$systemd_unit" ]]; then
     cat >> "$spec_file" <<SPEC
 mkdir -p %{buildroot}/lib/systemd/system
-cp $systemd_unit %{buildroot}/lib/systemd/system/
+cp %{_sourcedir}/$(basename "$systemd_unit") %{buildroot}/lib/systemd/system/
 SPEC
   fi
 
   cat >> "$spec_file" <<SPEC
 mkdir -p %{buildroot}/usr/share/doc/$pkg_name
-cp -r README.md %{buildroot}/usr/share/doc/$pkg_name/ 2>/dev/null || true
+cp -r %{_sourcedir}/README.md %{buildroot}/usr/share/doc/$pkg_name/ 2>/dev/null || true
 
 %files
 /usr/local/bin/$pkg_name