Rollup merge of #138533 - Kobzol:try-job-auto-tests, r=marcoieni

Only use `DIST_TRY_BUILD` for try jobs that were not selected explicitly

Some CI jobs (x64 Linux, ARM64 Linux and x64 MSVC) use the `opt-dist` tool to build an optimized toolchain using PGO and BOLT. When performing a default try build for x64 Linux, in most cases we want to run perf. on that artifact. To reduce the latency of this common use-case, `opt-dist` skips building several components not needed for perf., and it also skips running post-optimization tests, when it detects that the job is executed as a try job (not a merge/auto job).

This is useful, but it also means that if you *want* to run the tests, you had to go to `jobs.yml` and manually comment this environment variable, create a WIP commit, do a try build, and then remove the WIP commit, which is annoying (in the similar way that modifying what gets run in try builds was annoying before we had the `try-job` annotations).

I thought that we could introduce some additional PR description marker like `try-job-run-tests`, but it's hard to discover that such things exist.

Instead, I think that there's a much simpler heuristic for determining whether `DIST_TRY_BUILD` should be used (that I implemented in this PR):
- If you do just ``@bors` try`, without any custom try jobs selected, `DIST_TRY_BUILD` will be activated, to finish the build as fast as possible.
- If you specify any custom try jobs, you are most likely doing experiments and you want to see if tests pass and everything builds as it should. The `DIST_TRY_BUILD` variable will thus *not* be set in this case.

In this way, if you want to run dist tests, you can just add the `try-job: dist-x86_64-linux` line to the PR description, and you don't need to create any WIP commits.

r? `@marcoieni`

1 files changed, 5 insertions, 7 deletions

diff --git a/src/ci/github-actions/jobs.yml b/src/ci/github-actions/jobs.yml
index 4888bf9f867..c4ee7a19825 100644
--- a/src/ci/github-actions/jobs.yml
+++ b/src/ci/github-actions/jobs.yml
@@ -82,15 +82,13 @@ envs:
     AWS_REGION: us-west-1
     TOOLSTATE_PUBLISH: 1
 
+  # Try builds started through `@bors try` (without specifying custom jobs
+  # in the PR description) will be passed the `DIST_TRY_BUILD` environment
+  # variable by citool.
+  # This tells the `opt-dist` tool to skip building certain components
+  # and skip running tests, so that the try build finishes faster.
   try:
     <<: *production
-    # The following env var activates faster `try` builds in `opt-dist` by, e.g.
-    # - building only the more commonly useful components (we rarely need e.g. rust-docs in try
-    #   builds)
-    # - not running `opt-dist`'s post-optimization smoke tests on the resulting toolchain
-    #
-    # If you *want* these to happen however, temporarily comment it before triggering a try build.
-    DIST_TRY_BUILD: 1
 
   auto:
     <<: *production