Reflect verbosity option changes for Makefile

[ken-matsui]

Prior to this patch, -q option was not propagated to the generated Makefile correctly:

$ poac b             
 Compiling <package name>
  Finished `dev` profile [unoptimized + debuginfo] target(s) in 4.83s

$ poac b -q
 Compiling <package name>

This is because Makefile is generated based on Poac's option and will not reflect the option until it is regenerated.

This patch instead generates Makefile, which takes option info dynamically. Also, this patch avoids printing Compiling <package name> when the target is cached.