Can't build anything after upgrade to gcc8

Can’t build anything after latest system upgrade to gcc8, get errors:

/usr/include/c++/8/cstdlib:75: error: stdlib.h: No such file or directory
 #include_next <stdlib.h>
               ^~~~~~~~~~

File exists in /usr/include/stdlib.h How to solve?

Is libstdc++6-devel-gcc8 installed? You may have to look in for /usr/include/c++/8/stdlib.h rather than the file in /usr/include.

Yes, installed, and the file exists in /usr/include/c++/8/stdlib.h as well. Some gcc installation/path bug which met very often:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70129

I was building Qt Creator. Seems problem was in wrong CLANG version. Builds fine now. You may close this for now. Sorry.