scripts/git: Ensure we don't have circular references

This is horrible but I'm running out of better ideas. We hit circular reference
issues which we were trying to avoid in the core HOSTTOOLS code. When building
the eSDK, there can be two copies of the script.

Therefore assume git will never be in a directory called scripts. This
fixes eSDK build failures.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 27de610a)
Signed-off-by: Steve Sakoman <steve@sakoman.com>