This is a second attempt atgitpython-developers#1906 and should resolve:-gitpython-developers#1905-google/oss-fuzz#10600PRgitpython-developers#1906 had the right idea but wrong implementation, and the differences betweenthe ClusterFuzz image that it was supposed to fix and the OSS-Fuzz image wherethe fix was tested led to the issue not being fully resolved.The root cause of the issue is the same: A Git executable is not globallyavailable in the ClusterFuzz container environment where OSS-Fuzz executesfuzz tests.gitpython-developers#1906 attempted to fix the issue by bundling the Git binary and usingGitPython's `git.refresh(<full-path-to-git-executable>)` method to set itinside the `TestOneInput` function of the test harness.However, GitPython attempts to set the binary at import time via its `__init__`hook, and crashes the test if no executable is found during the import.This issue is fixed here by setting the environment variable that GitPythonlooks in before importing it, so it's available for the import. This was testedby setting the `$PATH` to an empty string inside the test files, whichreproduced the crash, then adding the changes introduced here with `$PATH` stillempty, which avoided the crash indicating that the bundled Git executable isworking as expected.