make: add fuzz-build and fuzz commands

make/fuzz_flags.mk

@@ -0,0 +1,34 @@
+FUZZPKG = brontide lnwire wtwire
+FUZZ_TEST_RUN_TIME = 30
+FUZZ_TEST_TIMEOUT = 20
+FUZZ_NUM_PROCESSES = 4
+FUZZ_BASE_WORKDIR = $(shell pwd)/fuzz
+
+# If specific package is being fuzzed, construct the full name of the
+# subpackage.
+ifneq ($(pkg),)
+FUZZPKG := $(pkg)
+endif
+
+# The default run time per fuzz test is pretty low and normally will be
+# overwritten by a user depending on the time they have available.
+ifneq ($(run_time),)
+FUZZ_TEST_RUN_TIME := $(run_time)
+endif
+
+# If the timeout needs to be increased, overwrite the default value.
+ifneq ($(timeout),)
+FUZZ_TEST_TIMEOUT := $(timeout)
+endif
+
+# Overwrites the number of parallel processes. Should be set to the number of
+# processor cores in a system.
+ifneq ($(processes),)
+FUZZ_NUM_PROCESSES := $(processes)
+endif
+
+# Overwrite the base work directory for the fuzz run. Can be used to supply any
+# previously generated corpus.
+ifneq ($(base_workdir),)
+FUZZ_BASE_WORKDIR := $(base_workdir)
+endif