gitpython: Failing on every run

I think the solution is to bundle git. I don't think we have git on our clusterfuzz instances.
It's failing with this error:
```
Traceback (most recent call last):
File "git/__init__.py", line 89, in
File "git/__init__.py", line 76, in refresh
File "git/cmd.py", line 392, in refresh
ImportError: Bad git executable.
The git executable must be specified in one of the following ways:
- be included in your $PATH
- be set via $GIT_PYTHON_GIT_EXECUTABLE
- explicitly set via git.refresh()

All git commands will error until this is rectified.

This initial warning can be silenced or aggravated in the future by setting the
$GIT_PYTHON_REFRESH environment variable. Use one of the following values:
- quiet|q|silence|s|none|n|0: for no warning or exception
- warn|w|warning|1: for a printed warning
- error|e|raise|r|2: for a raised exception

Example:
export GIT_PYTHON_REFRESH=quiet

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "fuzz_config.py", line 20, in
File "PyInstaller/loader/pyimod03_importers.py", line 495, in exec_module
File "git/__init__.py", line 91, in
ImportError: Failed to initialize: Bad git executable.
The git executable must be specified in one of the following ways:
- be included in your $PATH
- be set via $GIT_PYTHON_GIT_EXECUTABLE
- explicitly set via git.refresh()

All git commands will error until this is rectified.

This initial warning can be silenced or aggravated in the future by setting the
$GIT_PYTHON_REFRESH environment variable. Use one of the following values:
- quiet|q|silence|s|none|n|0: for no warning or exception
- warn|w|warning|1: for a printed warning
- error|e|raise|r|2: for a raised exception

Example:
export GIT_PYTHON_REFRESH=quiet

[1090381] Failed to execute script 'fuzz_config' due to unhandled exception!
"
```