bzip2: generate a relocatable shared lib on macOS

[SpaceIm]

Specify library name and version: lib/1.0

see conan-io/hooks#376

---

• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[SpaceIm]

Now bzip2 shared in install tree is relocatable:

otool -L libbz2.1.0.8.dylib

libbz2.1.0.8.dylib:
	@rpath/libbz2.1.dylib (compatibility version 1.0.0, current version 1.0.8)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1311.0.0)

without this fix, it's wrong:

libbz2.1.0.8.dylib:
	libbz2.1.dylib (compatibility version 1.0.0, current version 1.0.8)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1311.0.0)

[conan-center-bot]

All green in build 2 (0bfe19fbd6da72e234a44d7c5f4b046396efb3ea):

• bzip2/1.0.8@:
  All packages built successfully! (All logs)

• bzip2/1.0.6@:
  All packages built successfully! (All logs)