[build] Allow fabrication outside git repository

Currently fabricate expects to be run from inside a git checkout so
that it can derive the version number from the git tags. This breaks
building cocopp / cocoex from a ZIP file download from GitHub.

Instead of erring out, this commit uses a default version number of
'99.0.1' for the build.

Fixes #2259

scripts/fabricate

@@ -137,7 +137,10 @@ def git_version(format="pep440"):
     '0.1-6015-ga0a3769' if not pep440 else '0.1.6015'
 
     """
-    res = git(['describe', '--tags']).lstrip("v").split("-")
+    try:
+        res = git(['describe', '--tags']).lstrip("v").split("-")
+    except subprocess.CalledProcessError:
+        res = ("99.0.0", "0", "0")
     if len(res) == 1: # Clean tagged release
         return res[0] # Strip leading v
     else: