This reverts commit d71611fb72, reversing
changes made to cae9272c92.
The update caused an issue on aarch64-linux where it's the default
compiler, many packages got broken (usually through `mariadb`; I think).
File lib/gcc/aarch64-unknown-linux-gnu/9.4.0/include/arm_acle.h
got unbalanced braces (look at `cplusplus` lines), e.g. see in
/nix/store/fvkdvx69sf8h99xgx0m42dzfd5ly5csr-gcc-9.4.0/
I don't know how exactly it happened, as in the source this header is OK
and hasn't even changed between 9.3.0 and 9.4.0. I assume that some
post-processing on headers got broken. Anyway, I don't have much
motivation to dig deeper here, but perhaps someone else will.
28e731742c