wireguard-tools: bump to 1.0.20200121

wireguard-tools: bump to 1.0.20200121

* Makefile: remove pwd from compile output
* Makefile: add standard 'all' target
* Makefile: evaluate git version lazily

Quality of life improvements for packagers.

* ipc: simplify inflatable buffer and add fuzzer
* fuzz: add generic command argument fuzzer
* fuzz: add set and setconf fuzzers

More fuzzers and a slicker string list implementation. These fuzzers now find
themselves configuring wireguard interfaces from scratch after several million
mutations, which is fun to watch.

* netlink: make sure to clear return value when trying again

Prior, if a dump was interrupted by a concurrent set operation, we'd try
again, but forget to reset an error flag, so we'd keep trying again forever.
Now we do the right thing and succeed when we succeed.

* Makefile: sort inputs to linker so that build is reproducible

Earlier versions of make(1) passed GLOB_NOSORT to glob(3), resulting in the
linker receiving its inputs in a filesystem-dependent order. This screwed up
reproducible builds.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>