SwiftLint2

Change `prefix_install` of `Makefile`

For Homebrew installation, RPATH should be following:
```
% otool -l /usr/local/bin/swiftlint
…
Load command 25
          cmd LC_RPATH
      cmdsize 104
         path @executable_path/../Frameworks/SwiftLintFramework.framework/Versions/Current/Frameworks (offset 12)
Load command 26
          cmd LC_RPATH
      cmdsize 48
         path @executable_path/../Frameworks (offset 12)
```