Use static rocksdb linkage on Mac [ECR-3324] (#1011)

RocksDB is linked statically on Mac to avoid problems with dynamic library resolving.
When dynamic linking is currently used, the app has a dependency on a particular
version of the library, with any new version breaking the installation.

It is required to set ROCKSDB_LIB_DIR prior to running package_app.sh.

(cherry picked from commit ae4593c)

Author: Ilya Bogdanov

CONTRIBUTING.md

@@ -22,6 +22,15 @@ You need to install the following dependencies:
   * [Stable Rust](https://www.rust-lang.org/tools/install).
   * The [system dependencies](https://exonum.com/doc/version/0.11/get-started/install/) of Exonum. 
   You do _not_ need to manually fetch and compile Exonum.
+  __Important__: On Mac OS it is necessary to install RocksDB
+  package and to set the environment variable `ROCKSDB_LIB_DIR`.
+  To install the package via Homebrew:
+  
+  ```bash
+  brew install rocksdb
+  export ROCKSDB_LIB_DIR=/usr/local/lib
+  ```
+  
   * For automatic packaging of the Exonum Java app you need [CMake](https://cmake.org/) installed in your system. 
   Also on Mac you need a [`coreutils`](https://formulae.brew.sh/formula/coreutils) package installed.
 
@@ -36,6 +45,7 @@ $ mvn install
 ```
 
 #### Building Exonum Java App
+
 Run:
 
 ```$sh

exonum-java-binding/CHANGELOG.md

@@ -57,7 +57,8 @@ the [migration guide](https://github.com/exonum/exonum-java-binding/blob/ejb/v0.
   `CommonTypeAdapterFactory`. `BlockTypeAdapterFactory` is renamed to `CoreTypeAdapterFactory`.
   `JsonSerializer#json` and `JsonSerializer#builder` register `CommonTypeAdapterFactory` 
   by default. `CoreTypeAdapterFactory` must be registered explicitly if needed. (#971)
-
+- Exonum Java App now uses static linkage for RocksDB on Mac OS. Installed RocksDB
+  is no more necessary to run the App. (#1011)
 
 ### Fixed
 - The default [`Transaction#info`][tx-info-07] implementation causing an error on `transaction`

exonum-java-binding/package_app.sh

@@ -44,6 +44,17 @@ function build-exonum-java-for-platform() {
 }
 
 function build-exonum-java-macos() {
+    # We use static linkage for RocksDB on Mac because dynamic linking
+    # on Mac does not work: the resulting app has a dependency on a _particular_
+    # version of the RocksDB library, hence, is incompatible with any updates
+    # to the library, even the patch ones. It is believed to be a Cargo issue
+    # or RocksDB build configuration issue, see ECR-3324.
+    export ROCKSDB_STATIC=1
+    # Check if ROCKSDB_LIB_DIR is set
+    if [ -z "${ROCKSDB_LIB_DIR:-}" ]; then
+      echo "Please set ROCKSDB_LIB_DIR"
+      exit 1
+    fi
     build-exonum-java-for-platform "@loader_path" "libjava_bindings.dylib"
 }