Added build instructions

git-svn-id: https://svn.code.sf.net/p/speed-dreams/code/trunk@7656 30fe4595-0a0c-4342-8851-515496e4dcbd

packaging/3rdParty-devel/readme.txt

@@ -13,11 +13,42 @@ Building the dependencies for Speed-Dreams makes use of CMake's ExternalProject
  You will need more than 1GB of free disk space for the build.
 
  Prerequisites:
- DirectX sDK (June 2010) - needed by SDL and possibly OpenAL
+ DirectX SDK (June 2010) - needed by SDL and possibly OpenAL
  http://www.microsoft.com/en-us/download/details.aspx?id=6812
 
  CMake version 3.4 or greater.
 
+ Building the 3rd Party dependencies for Windows
+
+ Get the code
+
+    Using Subversion:
+        svn co https://svn.code.sf.net/p/speed-dreams/code/trunk/packaging/3rdParty-devel C:\src\3rdParty-devel
+
+    If you already have the speed-dreams code:
+        copy <Path-to sd-code>\packaging\3rdParty-devel\*.* C:\src\3rdParty-devel
+
+    Important - Keep the path short ie: C:\src\3rdParty-devel
+    The building of OpenSceneGraph with CMake's ExternalProject_Add creates quite a deep tree and the build may fail. 
+
+ CMake CLI Build
+
+    Make a directory under the source directory (C:\src\3rdParty-devel)
+        mkdir build-vs2015-release
+    
+    Change to the new directory:
+        cd build-vs2015-release
+
+    Generate the build system:
+        cmake -G "Visual Studio 14 2015" .. -D CMAKE_BUILD_TYPE=Release -A Win32
+
+    Build the package:
+        cmake --build . --target PACKAGE --config Release
+
+ Note:
+   To build with VS2019 on Windows 7 or 8x, you may need to add -D CMAKE_SYSTEM_VERSION=10.0 to the command line:
+         cmake -G "Visual Studio 16 2019" .. -D CMAKE_BUILD_TYPE=Release -D CMAKE_SYSTEM_VERSION=10.0 -A Win32
+
   =============================================================================
  OS X
  TODO
@@ -25,4 +56,7 @@ Building the dependencies for Speed-Dreams makes use of CMake's ExternalProject
    =============================================================================
  Linux
  TODO
+
+
+