custom compiler c++11 support and gcc-like compiler extra headers

I have external toolchain based on Linaro gcc.
I tried to make everything right under qt for it but faced with two issues:

1) In case when i configure it as
'gcc-like' compiler
i see that some includes could not be found on parsing stage therefore I cannot parse some system classes /etc.

2) In case when i configure it as custom compiler i could add all includes, but:

even with defines
_linux_
_GNUC_=4
_GNUC_MINOR_=8
__cplusplus=201103

i could not make it to treat some c+11 keywords from my valid c+11 project.

BTW issue is under
Qt Creator 4.12.3
Based on Qt 5.14.2 (GCC 5.3.1 20160406 (Red Hat 5.3.1-6), 64 bit)

Built on Jun 16 2020 04:15:35

From revision 48e46132e3

but i cannot pick 4.12.3

=========================
i propose:

1) to be able to add edxtra include files even for non-custom compilers

2) be able to turn on c++11 support for custom ones. Pictures with custom against normal are attached