Update VxWorks 6.9 toolchain

[jphickey]

Describe the bug
The example toolchain file for vxworks 6.9 does not work "out of the box" in combination with the current MCP750 PSP.

Need to add additional include paths and other paths under WIND_BASE / WIND_HOME environment variables to more easily adapt to other platforms.

To Reproduce
See nasa/PSP#181

Additional context
Proposing alternative solution this issue via cmake toolchain file modifications.

Reporter Info
Joseph Hickey, Vantage Systems, Inc.