fuzz: if the caller of our makefile sets CC and CXX, trust them
This should fix the broken fuzzing build, because we've been
explicitly using clang++ but are now being given a CXX=afl++, which
does extra stuff.
Differential Revision: https://phab.mercurial-scm.org/D10066
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true