[PySide] Problems with clang 10. Qt 5.13.2, and pyside2, git branch 5.13.2

[Kacvinsky, Tom]

I am trying to build PySide2 (with tag 5.13.2) with Qt 5.13.2.  Was able to get Qt built fine,
and I built LLVM/clang from source as I have a custom location of GCC.  On CentOS 7.6

I still had problems finding stddef.h (included by cstddef), until I set the clang environment
variable CPATH (which was set to the include paths generated by "gcc -v -xc++ /dev/null")

That fixed the problem with cstddef, but now I have this problem:

/home/BUILD64/bin/gcc-8.3.0-2/include/c++/8.3.0/cstdlib:75:15: fatal error: stdlib.h: No such file or directory
 #include_next <stdlib.h>
               ^~~~~~~~~~
Not sure if this is a PySide2 problem or a LLVM (version 10, BTW) problem.  I just find it
out that the cstddef issue was fixed but not the cstdlib issue, as they have a similar chain
of includes.

Any ideas would be appreciated.  If you need further information, please let me know
and I will provide it.

Regards,

Tom