support/testing/infra/builder.py: fix missing $HOME during build

When running a test that uses host-python-setuptools using the Buildroot
Docker image, for example running the following command,

> ./utils/docker-run ./support/testing/run-tests -o output -s -k tests.package.test_python_pytest.TestPythonPy3Pytest

The build fails with the following error,

>   File "/home/blmaier/buildroot/output/TestPythonPy3Pytest/build/host-python-setuptools-69.2.0/setuptools/_distutils/dist.py", line 354, in _gen_paths
>     yield pathlib.Path('~').expanduser() / filename
>           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>   File "/home/blmaier/buildroot/output/TestPythonPy3Pytest/host/lib/python3.11/pathlib.py", line 1385, in expanduser
>     raise RuntimeError("Could not determine home directory.")
> RuntimeError: Could not determine home directory.
>
> ERROR Backend subprocess exited when trying to invoke get_requires_for_build_wheel

Python setuptools is looking for $HOME but failing to find it.

Signed-off-by: Brandon Maier <brandon.maier@collins.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

support/testing/infra/builder.py

@@ -52,7 +52,10 @@ class Builder(object):
                            "> end defconfig\n")
         self.logfile.flush()
 
-        env = {"PATH": os.environ["PATH"]}
+        env = {
+            "PATH": os.environ["PATH"],
+            "HOME": os.environ["HOME"]
+        }
         env.update(make_extra_env)
 
         cmd = ["make",
@@ -79,7 +82,11 @@ class Builder(object):
         in the environment that calls make.
         e.g. make_extra_env={"BR2_DL_DIR": "/path"}
         """
-        env = {"PATH": os.environ["PATH"]}
+        env = {
+            "PATH": os.environ["PATH"],
+            "HOME": os.environ["HOME"]
+        }
+
         if "http_proxy" in os.environ:
             self.logfile.write("Using system proxy: " +
                                os.environ["http_proxy"] + "\n")