The bundle build tasks temporarily relocate Gemfile and gemspecs to
temporary directories when packing bundles. For this to work, we can't
depend on the Gemfile/gemspec exisiting in a specific location relative
to other code.
This allows specifying the project root via the MSP_ROOT environment
variable. If you do not specify MSP_ROOT, the behavior is unchanged.
MSP-10684
MSP-9653
Add gemspec for metasploit-framework so that pro can declare it as a
proper dependency. DO NOT release metasploit-framework to rubygems: it
is 47 MB and would be not be nice to their servers.