Under Debian, the libbz2.so SONAME is libbz2.so.1.0, so ld links to this
version of libbz2. Debian has symlinks from libbz2.so.1 and libbz2.so.1.0 to
libbz2.so.1.0.x. RedHat however does not have the libbz2.so.1.0 symlink
so linking fails at runtime.
This commit fixes the problem by linking to libbz2 statically on Linux.
This does not bloat the updater library too much as libbz2 is only 70K
(measured on Ubuntu 11.04).
This allows the updater to work on older Windows XP systems
without the VC++ 2008 runtime redistributable installed.
* Add statically linked pre-built versions of the zlib and
bzip2 libraries.
This increases the size of the updater executable by 200KB
to ~400KB on Windows.
The zlib build system is not integrated with the updater's build
system. Rather than write a small CMakeLists.txt for the build,
this commit just adds a pre-built version of zlib
