the doc for android/java custom build. (#260)

* the doc for android/java custom build.

* Update custom_build.md

* Update custom_build.md

* Update custom_build.md

cmake/externals/opencv.cmake

@@ -1,4 +1,3 @@
-set(BUILD_ZLIB OFF CACHE INTERNAL "")
 set(BUILD_TIFF OFF CACHE INTERNAL "")
 set(BUILD_OPENJPEG OFF CACHE INTERNAL "")
 set(BUILD_JASPER OFF CACHE INTERNAL "")
@@ -119,3 +118,6 @@ if (OCOS_ENABLE_OPENCV_CODECS)
     list(APPEND opencv_INCLUDE_DIRS ${OPENCV_MODULE_opencv_imgcodecs_LOCATION}/include)
     list(APPEND opencv_LIBS opencv_imgcodecs)
 endif()
+
+# unset it to avoid affecting other projects.
+unset(EXECUTABLE_OUTPUT_PATH CACHE)

docs/custom_build.md

@@ -0,0 +1,32 @@
+# Build ONNX Runtime with onnxruntime-extensions for Java package
+
+*The following step are demonstrated for Windows Platform only, the others like Linux and MacOS can be done similarly.*
+
+> Android build was supported as well; check [here](https://onnxruntime.ai/docs/build/android.html#cross-compiling-on-windows) for arguments to build AAR package.
+
+## Tools required
+1. install visual studio 2022 (with cmake, git, desktop C++)
+2. install miniconda to have Python support (for onnxruntime build)
+3. OpenJDK: https://docs.microsoft.com/en-us/java/openjdk/download
+		(OpenJDK 11.0.15 LTS)
+4. Gradle: https://gradle.org/releases/
+		(v6.9.2)
+
+## Commands
+Launch **Developer PowerShell for VS 2022** in Windows Tereminal
+```
+	. $home\miniconda3\shell\condabin\conda-hook.ps1
+	conda activate base
+
+	$env:JAVA_HOME="C:\Program Files\Microsoft\jdk-11.0.15.10-hotspot"
+	# clone ONNXRuntime
+	git clone -b rel-1.12.0 https://github.com/microsoft/onnxruntime.git onnxruntime
+
+	# clone onnxruntime-extensions
+	git clone https://github.com/microsoft/onnxruntime-extensions.git onnxruntime_extensions
+
+	# build JAR package in this folder
+	mkdir ortall.build
+	cd ortall.build
+	python ..\onnxruntime\tools\ci_build\build.py --config Release --cmake_generator "Visual Studio 17 2022" --build_java --build_dir .  --use_extensions --extensions_overridden_path "..\onnxruntime-extensions"
+```