Issues:

1. The IncrediBuild warning "import directives in the precompiled header should use the no_implementation attribute. See FAQ section in documentatio n for more details." Is shown, relating to code inside a multi-line comment. 
2. When changing a file referenced by an #include statement that appears in the scope of an #ifdef statement that does not evaluate to TRUE, running an incremental build will result in the referencing file being recompiled. 
   

Cause:

IncrediBuild parses all preprocessor reference files, including conditional statements within your source code. The warning described occurs in cases where an #import statement appears within one of these parsed portions of code. If yours source code includes many #include statements where you have multiple coniditional statements, removing thee lines of code may have an improvement on compilation speed.

Fix:

Add the "no_implementation" attribute to the #import statements you have used, or just delete the #import directives from your pre-compiled header files. 

 Also, please refer to the following link and search for "I'm getting the following warning: "IncrediBuild: build system warning: #import directives in the precompiled header should use the no_implementation attribute. See FAQ section in documentation for more details.". What's wrong?" for a more detailed reference.

http://www.incredibuild.com/webhelp/webframe.htm#detailed_reference7.html