This change attempts to leverage as many of the existing tests under compiler-rt/test/fuzzer as possible for testing remote fuzzing. It introduces a new set of "check" targets, "check-fuzzer-remote-${arch}", that signal to the llvm-lit configuration to modify the 'compiler' and 'run commands. It builds two binaries for each test instead of one: a remote fuzzer that receives its test inputs via IPC, and a fuzzer engine proxy that starts the remote fuzzer, sends it inputs, and collects coverage from it.
This is the 20 change in a chain to enable remote fuzzing support.