Use a shell script over a makefile

Simpler build system, easier to read.

build.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env sh
+
+set -xe
+
+GFLAGS="-Wall -Wextra -Wswitch-enum -std=c++17"
+DFLAGS="-ggdb -fsanitize=address -fsanitize=undefined"
+CFLAGS="$GFLAGS $DFLAGS"
+LIBS="-lraylib -lm"
+
+c++ $CFLAGS -o cw_tree.out src/numerics.cpp src/main.cpp $LIBS