Improve the build system

[jtraglia]

This makes a few notable improvements to the build system:

• If the blst submodule has been updated, it will re-build & copy files.
• Do not build object files individually. The build prints won't show now.
  • I kind of liked this though, because it ensured imports were correct.
• Add prints for each rule, so the developer knows what's going on.
• Also, fix build for profiler (it was using too much stack).
• Also, build blst in the Java bindings. If the library didn't exist, it would error.

[jtraglia]

Should be non-controversial. George said it worked for him last week. Going to merge.