Fix build without git clone in cloned directory

[pkubaj]

FreeBSD uses git to manage Ports Tree. Tesseract, when building from the Ports Tree, is built from a tarball that doesn't have .git and then git describe is ran on top of the Ports Tree.

[stweil]

So the whole Tesseract source tree is a subdirectory of some directoy structure which is managed with Git? Will your patch also work when configure is running out-of-tree?

[pkubaj]

Indeed it is in a subdirectory managed by git. Running configure out of tree probably won't work, but I don't think anyone does that (I certainly have never done that).

[stweil]

I nearly never run builds in-tree, but usually have a build directory somewhere below the source root, so git describe works fine. Supporting out-of-tree builds is important in my opinion

[stweil]

Thank you. I tested the commit. It also works fine with out-of-tree builds.