fix build for docsrs

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "ng-rocksdb"
 description = "Rust wrapper for Facebook's RocksDB embeddable database, fork for Nextgraph.org"
-version = "0.21.0"
+version = "0.21.0-ngpreview.1"
 edition = "2018"
 rust-version = "1.60"
 authors = ["Tyler Neely <t@jujit.su>", "David Greenberg <dsg123456789@gmail.com>"]

librocksdb-sys/build.rs

@@ -460,7 +460,9 @@ fn update_submodules() {
 
 fn main() {
     if !Path::new("librocksdb-sys/rocksdb/AUTHORS").exists() {
-        update_submodules();
+        println!("cargo:rustc-cfg=NG_ROCKS_DB_NOT_FOUND");
+        return;
+        //update_submodules();
     }
     let target = env::var("TARGET").unwrap();
     if target.contains("openbsd") {

src/lib.rs

@@ -72,6 +72,9 @@
     clippy::from_over_into,
 )]
 
+#[cfg(all(not(doc), NG_ROCKS_DB_NOT_FOUND))]
+std::compile_error!("empty librocksdb-sys/rocksdb directory");
+
 #[macro_use]
 mod ffi_util;