Rework the build system to be more modular

Split most of the work off into make/base.mk and allow for easy wrappers
to be created around that that can build with different instrumentation
in their own build directory.

Create wrappers for the following:
 - release build
 - debug build
 - afl++ fuzzing build
 - static analysis with clang
 - clang memory sanitizer
 - clang address/undefined sanitizer

make/afl.mk

@@ -0,0 +1,14 @@
+.PHONY: fuzz distclean
+
+CC=afl-clang-fast
+LD=afl-clang-fast
+BUILD_DIR=build/afl/
+
+-include make/base.mk
+
+fuzz: $(BUILD_DIR)$(TARGET)
+	mkdir -p reports/afl
+	afl-fuzz -i tests/input -o reports/afl -m none -- ./$< -tokens @@
+
+distclean: clean
+	rm -rf reports/afl