[analyzer] Show full analyzer invocation for reproducibility in HTML reports

Analyzing problems which appear in scan-build results can be very
difficult, as after the launch no exact invocation is stored, and it's
super-hard to launch the debugger.
With this patch, the exact analyzer invocation appears in the footer,
and can be copied to debug/check reproducibility/etc.

rdar://35980230

llvm-svn: 323245