Add a README.md detailing how to build the Native Binaries

Author: adamretter

exist-service/bin/README.md

@@ -0,0 +1,43 @@
+# Note on Native Binaries
+
+## Windows Binary
+The Windows Binary is taken directly from the native binaries for Windows package provided by the Apache Commons Daemon project. For example:
+```
+wget https://dlcdn.apache.org/commons/daemon/binaries/windows/commons-daemon-1.3.3-bin-windows.zip
+unzip commons-daemon-1.3.3-bin-windows.zip
+```
+
+## macOS Binary
+The macOS Binary is compiled as a Universal Binary for x86_64 and arm64 from the native source code for unix provided by the Apache Commons Daemon project.
+It is compiled for a minimum version of 10.13 of macOS so as to provide some backwards compatibility.
+
+For example:
+
+```bash
+wget https://dlcdn.apache.org/commons/daemon/source/commons-daemon-1.3.3-native-src.tar.gz
+tar zxvf commons-daemon-1.3.3-native-src.tar.gz
+cd commons-daemon-1.3.3-native-src/unix
+export CFLAGS="-mmacosx-version-min=10.13 -arch x86_64 -arch arm64"
+export LDFLAGS="-mmacosx-version-min=10.13 -arch x86_64 -arch arm64"
+./configure
+make
+```
+
+## Linux Binary
+The Linux binary is compiled for x86_64 from the native source code for unix provided by the Apache Commons Daemon project.
+It is compiled for a minimum glibc of 2.17 so as to provide some backwards compatibility between Linux distributions.
+
+CentOS 7 provides a glibc 2.17. If you have Docker, you can build it using the following example:
+
+```bash
+wget https://dlcdn.apache.org/commons/daemon/source/commons-daemon-1.3.3-native-src.tar.gz
+tar zxvf commons-daemon-1.3.3-native-src.tar.gz
+docker run -it -v /tmp/commons-daemon-1.3.3-native-src/unix:/commons-daemon-src centos:7
+yum install -y gcc make libcap-devel java-1.8.0-openjdk-headless java-1.8.0-openjdk-devel
+cd /commons-daemon-src
+export CFLAGS=-m64
+export LDFLAGS=-m64
+export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk
+./configure
+make
+```