Update Java API repo to include building from source doc

These steps were't migrated to Academy, so we're including them here.

Author: nickvigilante

README.md

@@ -7,8 +7,8 @@
 
 ## Quick Links
 
-- Installation: [https://docs.tiledb.com/developer/installation/building-from-source/java](https://docs.tiledb.com/developer/installation/building-from-source/java)
-- Full developer documentation for all APIs and integrations: [https://docs.tiledb.com/main/](https://docs.tiledb.com/main/)
+- Installation: [docs/building-from-source.md](docs/building-from-source.md)
+- Full developer documentation for all APIs and integrations: [https://cloud.tiledb.com/academy](https://cloud.tiledb.com/academy)
 
 ## Development Notes
 

docs/building-from-source.md

@@ -0,0 +1,47 @@
+# Building TileDB-Java from Source
+
+## Dependencies
+
+To build the JNI extension, you need to install the following:
+
+* Cmake (>=3.3)
+* JDK (>=1.8)
+
+## Build
+
+To build the library with the native library bundled in run:
+
+```bash
+./gradlew assemble
+```
+
+This will create the TileDB JNI library `build/tiledb_jni/libtiledbjni.dylib`. This will also download and build the TileDB core library if it is not found installed in a global system path, and place it in `build/externals/install/lib/libtiledb.dylib`.
+
+If you wish to build with a custom version of the TileDB core library, you can define the environment variable `TILEDB_HOME`, e.g.:
+
+```bash
+env TILEDB_HOME=/path/to/TileDB/dist ./gradlew assemble
+```
+
+Note that if you build with a custom native TileDB library, it will only be bundled into the jar if the native static library was produced.
+
+### Properties
+
+If TileDB is not globally installed in the system where the JNI library is being compiled, the TileDB core Library will be compiled. There are multiple properties which can be configured, including S3 and HDFS support.
+
+See [gradle.properties](https://github.com/TileDB-Inc/TileDB-Java/blob/master/gradle.properties) for all properties which can be set for building.
+
+The properties can be set via the `-P` option to `gradlew`:
+
+```bash
+./gradlew -P TILEDB_S3=ON -P TILEDB_VERBOSE=ON assemble
+```
+
+### Tests
+
+To run the tests use:
+
+```bash
+./gradlew test
+```
+