Setting both SNCSEQ and INSTALL_LOCATION causes build to fail

[exzombie]

When SNCSEQ is set in RELEASE, which typically happens when using the include ../../RELEASE.local mechanism, installing into INSTALL_LOCATION fails. The symptom is that RULES_SNCSEQ is installed into the $(INSTALL_LOCATION)/cfg directory, but the build at some point expects to find it in the $(INSTALL_LOCATION)/configure directory.

The cause is a backwards compatibility shim that the sequencer has in RULES_BUILD, which makes it compatible with EPICS base earlier than 3.15. Two solutions were discussed:

• Adding an ifndef BASE_3_15 guard to RULES_BUILD
• Making RULES_BUILD a copy of RULES_SNCSEQ

It is not yet clear which approach is better.

[anjohnson]

@bfrk if you choose the ifndef BASE_3_15 route that might not be the right release version to use. Looking more closely it looks like the cfg/RULES_* were first included in R3.14.10, 3fb737a or nearby so maybe it should be ifndef RELEASE_CFG_CONFIGS which I think will detect the right release, although maybe not quite the right commit.