TT#154401 build needs a $HOME dir

> virtualenv --python=python3
>  /build/repoapi-0.4.3+0~20211207150142.636+bullseye~1.gbpc1b960/venv_prod
> source /build/repoapi-0.4.3+0~20211207150142.636+bullseye~1.gbpc1b960/venv_prod/bin/activate && \
>  pip3 install -r ./requirements/prod.txt | tee install.log
> [snip]
> Building wheels for collected packages: python-crontab, python-ldap,
>   django-jsonify, django-object-tools, openapi-codec, drfapikey, psycopg2, coreschema
>  WARNING: Building wheel for python-crontab failed: [Errno 13]
> Permission denied: '/nonexistent'
>   WARNING: Building wheel for python-ldap failed: [Errno 13] Permission
> denied: '/nonexistent'
>   WARNING: Building wheel for django-jsonify failed: [Errno 13]
> Permission denied: '/nonexistent'
>   WARNING: Building wheel for django-object-tools failed: [Errno 13]
> Permission denied: '/nonexistent'
>   WARNING: Building wheel for openapi-codec failed: [Errno 13]
> Permission denied: '/nonexistent'
>   WARNING: Building wheel for drfapikey failed: [Errno 13] Permission
> denied: '/nonexistent'
>   WARNING: Building wheel for psycopg2 failed: [Errno 13] Permission
> denied: '/nonexistent'
>   WARNING: Building wheel for coreschema failed: [Errno 13] Permission
> denied: '/nonexistent'
> Failed to build python-crontab python-ldap django-jsonify
>  django-object-tools openapi-codec drfapikey psycopg2 coreschema
> ERROR: Could not build wheels for python-ldap which use PEP 517 and
>  cannot be installed directly

Change-Id: I8e51d32b0d18d87a9d2f722797da13d085e420e0

debian/rules

@@ -3,6 +3,8 @@
 # Uncomment this to turn on verbose mode.
 #export DH_VERBOSE=1
 
+export HOME=$(CURDIR)/$(BUILDDIR)
+
 %:
 	dh $@