hmm. can you try a kernel built with build.sh kernel=? ie, the "cross compiler" toos, vs. the compiler in /usr/bin.
if that also fails, we might have to bisect-by-object to see which object is faulty. ie, copy 1/2 the .o from gcc6 and half from gcc7 into the build, relink and try that kernel. if it works, 1/2 the remaining gcc7 files and repeat until failure indicates just one file. sometimes it can be multiple files. .mrg.
