1046 - #if expression cannot start with boolean operator.

Description
The first token in an #if expression should be a define (that exists or not).
Example
Config:
#if &&AAA #endif
Output:
c:\test\fbuild.bff(1,5): FASTBuild Error #1046 - #if expression cannot start with boolean operator. #if &&AAA ^ \--here
Fix:
#if AAA && BBB #endif