fixup! build(py-docker): Merge conflict resolution delete

Exposed in GitLab CI:

    Makefile:1680: warning: undefined variable 'TOX_BUILD_PREREQS'

Makefile

@@ -269,6 +269,7 @@ DOCKER_VARIANTS=$(foreach language,$(DOCKER_LANGUAGES),$(DOCKER_OSES:%=%-$(langu
 DOCKER_DEFAULT=$(DOCKER_OS_DEFAULT)-$(DOCKER_LANGUAGE_DEFAULT)
 endif
 export DOCKER_VARIANT?=$(firstword $(DOCKER_VARIANTS))
+DOCKER_VARIANT_HOST=$(DOCKER_OS_DEFAULT)-$(PYTHON_HOST_ENV)
 DOCKER_DEFAULT_VAR=./var-docker/$(DOCKER_DEFAULT)
 DOCKER_OS_DEFAULT_VAR=./var-docker/$(DOCKER_OS_DEFAULT)
 export DOCKER_BRANCH_TAG=$(subst /,-,$(VCS_BRANCH))
@@ -308,6 +309,9 @@ DOCKER_IMAGES+=$(DOCKER_IMAGE_DOCKER)
 endif
 export DOCKER_PASS?=
 DOCKER_COMPOSE_RUN_CMD=docker compose run --rm -T --quiet-pull
+ifeq ($(DOCKER_VARIANT),$(DOCKER_VARIANT_HOST))
+TOX_BUILD_PREREQS=./var-docker/$(DOCKER_VARIANT_HOST)/log/requirements/build.txt.log
+endif
 TEST_CODE_PREREQS=./var/log/build-pkgs.log
 
 # Run Python tools in isolated environments managed by Tox: