Building Andoid AOSP 7.x for Grouper up to now I was using gcc 4.9 for building the kernel. The kernel was stable, working fine and I had no issues. But almost each time when I tried to integrate a new feature / or changed the configuration of the kernel starting the compiled kernel resulted in a bootloop ... :-( First I thought it was related to compatibility issues between Nougat and SuperSU as I was patching the kernel when installing it on my device. I started a deeper analysis and found out that even booting the kernel without modifications lead to a bootloop. I was a bit irritated and was searching the internet and found Linus Torvalds wettert gegen Compiler-Collection GCC 4.9 and Linus Torvalds: "GCC 4.9.0 Seems To Be Terminally Broken" which made we wonder whether I ran into a similar situation. I changed the compiler to be used for kernel building to GCC 4.8 and voilá ... it worked!
Conclusion: do not use gcc 4.9 for kernel compilation it will mess up everything.