RFC: Increasing minimum GCC version

[Wilco Dijkstra]

Hi,

It has been almost 6 years since we increased the minimum GCC version to 6.2.
There are now various targets that prefer a much newer GCC to support new
features. Similarly generic features like static-pie need a newer GCC.
As a result, it's reasonable to increase the minimum version - I would suggest
GCC10 or GCC11 (note GCC11.5 is already the final release). This would allow
removal of a fair amount of GNU_PREREQ checks in C files/testcases and various
configure checks.

On a related note, we still have various __GNU_PREREQ (2, 4) in our headers.
Does anyone ever test such ancient compilers/binutils still work with GLIBC?
At which point do we consider them obsolete? Would it be reasonable to also
set a minimum version here which trails the minimum GLIBC build compiler by
say 5 years?

Wilco