test-release.sh: Add option to use ninja

Allow the use of ninja instead of make. This is useful on some
platforms where we'd like to be able to limit the number of link jobs
without slowing down the other steps of the release.

This patch adds a -use-ninja command line option, which sets the
generator to Ninja both for LLVM and the test-suite. It also deals with
some differences between make and ninja:
* DESTDIR handling - ninja doesn't like this to be listed after the
  target, but both make and ninja can handle it before the command
* Verbose mode - ninja uses -v, make uses VERBOSE=1
* Keep going mode - make has a -k mode, which builds as much as possible
  even when failures are encountered; for ninja we need to set a hard
  limit (we use 100 since most people won't look at 100 failures anyway)

I haven't tested with gmake.

llvm-svn: 353685