Compiling 6.0.16 on CentOs 6.x with devtoolset

Hi All,
I need KeyDB on CentOs 6, and with the specfile having systemd, I’m compiling from source.

I get the following error:
CC redis-cli.o
In file included from fastlock.h:3,
from ae.h:40,
from redis-cli.c:63:
fastlock.h:88:15: error: expected declaration specifiers or ‘…’ before ‘__builtin_offsetof’
88 | static_assert(offsetof(struct fastlock, m_ticket) == 64, “ensure padding is correct”);
| ^~~~~~~~
In file included from ae.h:40,
from redis-cli.c:63:
fastlock.h:88:58: error: expected declaration specifiers or ‘…’ before string constant
88 | static_assert(offsetof(struct fastlock, m_ticket) == 64, “ensure padding is correct”);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
make[1]: *** [Makefile:354: redis-cli.o] Error 1

I’ve tried using:
devtoolset-7
devtoolset-8
devtoolset-9

All give the same error.

Update: I opened this as a bug: https://github.com/JohnSully/KeyDB/issues/260