ci(fallback): don't fall back to local Rust build if precompiled asset not available

install-rust-fil-sector-builder

@@ -19,6 +19,7 @@ if download_release_tarball tarball_path "${subm_dir}"; then
 
     cp "${tmp_dir}/bin/paramcache" .
 else
+    if [ $CI = "true" ]; then
         (>&2 echo "failed to find or obtain precompiled assets for ${subm_dir} - falling back to local build")
         build_from_source "${subm_dir}"
 
@@ -30,4 +31,8 @@ else
         find "${subm_dir}" -type f -name sector_builder_ffi.pc -exec cp -- "{}" . \;
 
         (>&2 echo "WARNING: paramcache was not installed - you may wish to 'cargo install' it")
+    else
+        (>&2 echo "build failed: could not obtain precompiled assets for ${subm_dir} - contact @laser or @dignifiedquire")
+        exit 1
+    fi
 fi