Enhance native build documentation and adjust CONTRIBUTING section

CONTRIBUTING.md

@@ -15,19 +15,17 @@ and other infrastructure for running OSGi-based systems.
 Information regarding source code management, builds, coding standards, and
 more.
 
-* https://projects.eclipse.org/projects/eclipse.equinox/developer
-
 The project maintains the following source code repositories
 
-* https://github.com/eclipse-equinox/equinox.binaries
 * https://github.com/eclipse-equinox/equinox
+* https://github.com/eclipse-equinox/equinox.binaries
 * https://github.com/eclipse-equinox/p2
 
 This project uses GitHub to track ongoing development and issues.
 
-* Search for issues: https://github.com/eclipse-equinox/equinox.binaries/issues
+* Search for issues: https://github.com/eclipse-equinox/equinox/issues
 * Search for historical issues: https://eclipse.org/bugs/buglist.cgi?product=Equinox
-* Create a new report: https://github.com/eclipse-equinox/equinox.binaries/issues/new
+* Create a new report: https://github.com/eclipse-equinox/equinox/issues/new
 
 Be sure to search for existing bugs before you create another one. Remember that
 contributions are always welcome!
@@ -39,6 +37,11 @@ and run:
 
 `mvn clean verify -Pbuild-individual-bundles -Pbree-libs -Ptck`
 
+### Building the native executable and launcher library binaries
+
+The source code to build the platform specific executables and launcher libraries for Equinox is located in [org.eclipse.equinox.executable.feature](features/org.eclipse.equinox.executable.feature).
+For details see its [README.md](features/org.eclipse.equinox.executable.feature/README.md).
+
 ## Eclipse Contributor Agreement
 
 Before your contribution can be accepted by the project team contributors must

NOTICE

@@ -26,7 +26,6 @@ SPDX-License-Identifier: EPL-2.0
 
 The project maintains the following source code repositories:
 
-* http://git.eclipse.org/c/equinox/rt.equinox.binaries.git
-* http://git.eclipse.org/c/equinox/rt.equinox.bundles.git
-* http://git.eclipse.org/c/equinox/rt.equinox.framework.git
-* http://git.eclipse.org/c/equinox/rt.equinox.p2.git
+* https://github.com/eclipse-equinox/equinox.git
+* https://github.com/eclipse-equinox/equinox.binaries.git
+* https://github.com/eclipse-equinox/p2.git

features/org.eclipse.equinox.executable.feature/README.md

@@ -1,9 +1,31 @@
 This feature contains the eclipse executables and includes the equinox launcher bundle and its fragments.
-It also host the native C source files to build the executable and launcher binaries for all supported platforms.
+It also hosts the native C source files to build the launcher executable and launcher library binaries for all supported platforms.
 
-## Building the native executable and launcher binaries
+The _Equinox launcher executable_ is the executable binary file that can be used launch an Equinox based applications like Eclipse and is for example named `eclipse.exe` (on Windows) or `eclipse` (on Linux and Mac).
+The _launcher library_ is the native dynamic/shared library (eclipse.dll, eclipse.so, ...) that contains the compiled native code called from the `JNIBridge` in [`org.eclipse.equinox.launcher`](../../bundles/org.eclipse.equinox.launcher).
 
-To just build the native binaries navigate to the `library/<window-system>` sub-directory of interest and run 
+# Building the native executable and launcher binaries
+
+## Required software
+
+The software listed below is required to build the Equinox native binaries on the current platform targeting the same OS and processor arch.
+
+- common
+    - a JDK 1.8 or later (more recent versions are usually not a problem)
+- Windows:
+    - Microsoft Visual C Compiler 2019 or later (earlier version maybe also work), the 'Visual Studio Community Edition' is sufficient.
+- Linux:
+    - GTK development files. The Package `libgtk-3-dev` is sufficient.
+- MacOS:
+    - XCode Command Line Tools (already present in XCode)
+
+## Running the build
+
+The simplest way to build and install the native binaries for the running platform is to launch the Maven launch-configuration
+named `Build-Equinox-native-binaries-for-running-platform` from this project (requires Eclipse M2E being installed).
+It assumes the [`equinox.binaries`](https://github.com/eclipse-equinox/equinox.binaries.git) repository is checked out located next to this repository and is named `equinox.binaries`.
+
+To just build the native binaries for a specific platform navigate to the `library/<window-system>` sub-directory of interest and run 
 - `./build.sh` for Linux or MacOS
 - `.\build.bat` for Windows.
 
@@ -18,3 +40,9 @@ The `install` target additionally moves the just built binaries into the `equino
 The environment variable `BINARIES_DIR` can be set to specify an alternative path of the `equinox.binaries` repository to which the built binaries are moved.
 To specify the exact directory where the native executable or launcher library is moved, set the variable `EXE_OUTPUT_DIR` respectively `LIB_OUTPUT_DIR`.
 For more options and details see the `build.sh/bat` files and corresponding make-files.
+
+### Cross compilation
+
+On some platforms cross-compilation for other CPU architecutres is possible by invoking the `build.sh/bat` scripts with an explicit `-arch <target-arch>` argument.
+Of course the required tools for the targeted architecture have to be available.
+For example on a Windows computer with x86_64 CPU, one can call `build.bat -arch aarch64 -java <path-to-arm-jdk>` to build the executable and launcher-library for Windows on ARM.