GitHub build occasionally fails to compile CHANGEST C

[RossPatterson]

I expect this is a GCC bug of some sort, because I can't see how the bREXX build tooling could cause it, but I want to document it for anyone who encounters it in the future. Under circumstances I can't determine, the BRXBUILD EXEC tool will fail to compile CHANGEST C in non-debug mode, reporting the following (see, e.g., https://github.com/RossPatterson/CMS-370-BREXX/actions/runs/11752424040/job/32743950423#step:5:356):

CMD IS EXEC BRXCOMP CHANGEST
Invalid character ' ' in fileID 'CHANGEST     '.
Unable to open input file.
Error 20 adding CSECT label.

The build goes on to compile everything else sucessfully, including compiling CHANGEST in debug mode. There is if #ifdef __DEBUG__ code in CHANGEST C (although some of its include files do have some). The build eventually fails when building BREXX TEXT, because there is no CHANGEST TEXT file to include in it.

I've had this happen on two different branches I created off the develop branch (at commit 94b9beb), but I've created at least a dozen that way, and the rest don't fail. Once a branch fails in this way, it seems to never recover - all future commits fail.