These diagnostics are emitted by lint2, and like all diagnostics from
lint2, they don't affect the exit status.
In libc, lint cannot handle the renamings from namespace.h, generating
many false positive diagnostics since 'libc_function' is used but
'_libc_function' is defined. Until this situation is handled properly,
suppress this diagnostic.
While here, re-enable lint in those cases where lint was skipped due to
a bug in interpreting abstract types, which was fixed in cgram.y 1.469
from 2023-08-02.
rillig