Enhancement: [broadcom platforms] syncd build always gets its dependencies from BRCM_XGS_SAI

[veronica-arista]

Is it platform specific

broadcom

Importance or Severity

Medium

Description of the enhancement

Each SAI implementation (BRCM_XGS_SAI, BRCM_DNX_SAI, etc) should have its own syncd build to account for differences in support between the different SAIs.

Current Behavior

When syncd is built for broadcom devices, the dependencies come from BRCM_XGS_SAI regardless of what SAI is used.

This is defined in sonic-buildimage/platform/broadcom/rules.mk:
$(SYNCD)_DEPENDS += $(BRCM_XGS_SAI) $(BRCM_XGS_SAI_DEV)
https://github.com/sonic-net/sonic-buildimage/blob/master/platform/broadcom/rules.mk#L57

Problems occur when the XGS_SAI contains a symbol undefined in other SAI implementations. E.g. the update to LIBSAIBCM_XGS_VERSION = 13.2.1.0 in #23091 introduced sai_query_stats_st_capability which is not defined in the currently used DNX and BRONCOS SAI implementations, causing errors on those devices:
INFO gbsyncd#supervisord: syncd /usr/bin/syncd: symbol lookup error: /usr/bin/syncd: undefined symbol: sai_query_stats_st_capability#015

Proposed Behavior

Have multiple syncd builds to correspond with each SAI.

[veronica-arista]

We are using the following workaround to get over the undefined symbol: sai_query_stats_st_capability
sonic-net/sonic-sairedis#1629