Every time a compiler major version is bumped, we run into this exact
same error:
===> Configuring for valgrind-3.10.1.20160113_7,1
...
checking for a supported version of gcc... no (10.0.0)
configure: error: please use gcc >= 3.0 or clang >= 2.9
Attempt to fix this for all versions in the future.
Other fix included: don't use undefined behavior to implement offsetof,
just use the official builtin function instead.
Approved by: zeising (maintainer)
MFH: 2020Q1
02b7825abf