Specify --git-dir when building perf targets to allow out-of-tree
builds using O=<build-dir>.

The shell command in `git archive' had to be modified to allow proper
file name expansion of the files listed in MANIFEST.
Signed-off-by: Nmatt mooney <mfm@muteddisk.com>
Signed-off-by: NMichal Marek <mmarek@suse.cz>