重新指定SOPC BUILDER硬核问题（版本8.1）

When building a Nios II C/C++ application project, the Nios II IDE references the SOPC Builder system file (.ptf) to create executable code that matches the target hardware. After creating a project based on a specific SOPC Builder system, if the .ptf file changes (as a result of modifications to the hardware design in SOPC Builder), the Nios II system library project must be rebuilt. The build process detects an out-of-date .ptf file, and automatically rebuilds the Nios II system library project.

If you want to re-target your project to a different SOPC Builder system, you need to create a new Nios II system library project. Edits to your program source code might be necessary if, for example, the peripherals are named differently in the new SOPC Builder system.