[build] Add INCLUDE_PTF config to skip PTF test containers

[rustiqly]

What I did

Add INCLUDE_PTF config knob (default: y) to gate building of docker-ptf and docker-ptf-sai test containers on the VS platform.

Why I did it

Build timing analysis (from instrumentation in #25643) shows that p4lang packages consume ~28 minutes of build time:

Package	Duration
p4lang-p4c	13m 34s
p4lang-bmv2	5m 08s
p4lang-pi	3m 53s
docker-dash-engine	2m 50s
dash-ha + libdashapi	1m 53s
docker-ptf + docker-ptf-sai	~2m
Total	~28 min

These packages are pulled in as dependencies of docker-ptf and docker-ptf-sai, which are test containers not included in the final switch image (SONIC_ALL does not reference them). They are only needed for PTF (Packet Test Framework) testing.

For developers who are building VS images for development/testing but not running PTF tests, skipping these saves significant build time.

How I did it

• Added INCLUDE_PTF ?= y to rules/config (default on, preserving current behavior)
• Wrapped docker-ptf.mk and docker-ptf-sai.mk contents in ifeq ($(INCLUDE_PTF),y) guards

To skip PTF containers, add to rules/config.user:

INCLUDE_PTF = n

For maximum build time savings, also disable DASH SAI:

INCLUDE_PTF = n
INCLUDE_VS_DASH_SAI = n

How I verified it

1. With INCLUDE_PTF=y (default): build includes docker-ptf, docker-ptf-sai, and all p4lang deps — same as current behavior
2. With INCLUDE_PTF=n: docker-ptf and docker-ptf-sai are excluded from SONIC_DOCKER_IMAGES, and their p4lang dependencies are not pulled into the build graph
3. Verified the VS image itself (sonic-vs.img.gz) does not reference docker-ptf — it is not in SONIC_ALL

[mssonicbld]

/azp run Azure.sonic-buildimage

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[mssonicbld]

/azp run Azure.sonic-buildimage

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Pull request overview

This PR introduces a new build configuration flag INCLUDE_PTF (default: y) to gate the building of PTF (Packet Test Framework) test containers on the VS platform. The change allows developers to skip building docker-ptf and docker-ptf-sai test containers, which transitively avoids building expensive p4lang dependencies (p4lang-p4c, p4lang-bmv2, p4lang-pi), saving approximately 28 minutes of build time. The PR is motivated by build timing analysis from #25643 that identified these test containers and their dependencies as significant build time consumers despite not being included in final switch images.

Changes:

• Added INCLUDE_PTF ?= y configuration variable with comprehensive documentation in rules/config
• Wrapped docker-ptf.mk and docker-ptf-sai.mk contents in conditional blocks to skip their definition when INCLUDE_PTF=n
• Default value of 'y' preserves current behavior for backward compatibility

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
rules/config	Adds INCLUDE_PTF configuration variable with default value 'y' and detailed documentation explaining purpose, benefits, and dependencies
platform/vs/docker-ptf.mk	Wraps all docker-ptf container definitions and registrations in ifeq ($(INCLUDE_PTF),y) conditional block
platform/vs/docker-ptf-sai.mk	Wraps all docker-ptf-sai container definitions and registrations in ifeq ($(INCLUDE_PTF),y) conditional block

[Copilot]

The current implementation wraps all lines including SONIC_BOOKWORM_DOCKERS assignment inside the conditional block. This deviates from the established pattern in the codebase where SONIC_*_DOCKERS are always added unconditionally, even for conditionally-included features.

For consistency with other docker images (e.g., docker-stp.mk, docker-iccpd.mk, docker-p4rt.mk), consider following this pattern:

1. Define DOCKER_PTF variable unconditionally (outside ifeq)
2. Add to SONIC_BOOKWORM_DOCKERS unconditionally (outside ifeq)
3. Only wrap SONIC_DOCKER_IMAGES assignment in the conditional

This pattern is documented in codebase memory: "Docker images always added to SONIC_*_DOCKERS unconditionally, even when conditionally included via feature flags" (citations: rules/docker-iccpd.mk, rules/docker-stp.mk, rules/docker-dash-ha.mk).

However, if PTF containers are truly test-only artifacts that should be completely excluded from the build graph when disabled, the current approach may be acceptable as a deviation from the standard pattern.

[Copilot]

Same pattern deviation as docker-ptf.mk. The current implementation wraps all assignments including SONIC_BOOKWORM_DOCKERS inside the conditional, which differs from the established convention where SONIC_*_DOCKERS are added unconditionally.

For consistency with the codebase pattern, consider moving the SONIC_BOOKWORM_DOCKERS assignment (line 14) outside the ifeq block. However, if these test containers should be completely excluded from the build when INCLUDE_PTF=n, the current approach may be intentional.

Suggested change

	SONIC_BOOKWORM_DOCKERS += $(DOCKER_PTF_SAI)
	endif
	endif
	SONIC_BOOKWORM_DOCKERS += $(DOCKER_PTF_SAI)