RFR: 7903920: Support building jtreg on FreeBSD

[Magnus Ihse Bursie]

On Fri, 24 Jan 2025 23:01:09 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

>> I don't have any strong opinions about this, but for FreeBSD's part it would actually be slightly better to let the shell find the binaries in $PATH. But it's not important for my progress now, so I figured I'd deal with it if it comes up :)
>
> Maybe the concern is becoming obsolete, but the general design focus of this and similar scripts was to lock down everything, and avoid any variation that might occur as a result of individuals setting non-standard values for PATH and similar path-related variables -- CLASSPATH anyone?
> 
> But, a reasonable compromise would be to limit the use of `which` to this file (`Defs.gmk`) and maybe to within suitable `ifeq ($(SYSTEM_UNAME), FreeBSD)` constructs.
> 
> That all being said, I would defer to the expertise and style-advice of folk like @magicus on the Build team,  but with some amount of caveat for overall style consistency, as much as is reasonable.

If the path is hardcoded as e.g. `/usr/bin/foo`, I tend to agree with you. That means that an official system tool is needed and confirmed working. However, hard-coding `/usr/local/bin/foo` is another matter altogether. It means there is no standard system tool that is working, and we presume the user has installed a "correct" tool locally.

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PR Review Comment: https://git.openjdk.org/jtreg/pull/237#discussion_r1929606154