Add portable feature for RocksDB build

Cargo.toml

@@ -34,6 +34,7 @@ bzip2 = ["librocksdb-sys/bzip2"]
 rtti = ["librocksdb-sys/rtti"]
 multi-threaded-cf = []
 serde1 = ["serde"]
+portable = ["librocksdb-sys/portable"]
 
 [dependencies]
 libc = "0.2"

librocksdb-sys/Cargo.toml

@@ -24,6 +24,7 @@ zstd = ["zstd-sys"]
 zlib = ["libz-sys"]
 bzip2 = ["bzip2-sys"]
 rtti = []
+portable = []
 
 [dependencies]
 libc = "0.2"

librocksdb-sys/build.rs

@@ -90,6 +90,10 @@ fn build_rocksdb() {
         config.define("USE_RTTI", Some("1"));
     }
 
+    if cfg!(feature = "portable") {
+        config.define("PORTABLE", Some("1"));
+    }
+
     config.include(".");
     config.define("NDEBUG", Some("1"));