cmd/bent/configs/suites: xgo/ixgo use buildmode

[visualfc]

No description provided.

[fennoai]

Review summary

Scope: single config change to cmd/bent/configs/suites.toml, repointing the XGo and iXGo suites at their main packages (cmd/xgo, cmd/ixgo) and adding BuildMode = "build".

The change is well-formed and internally consistent:

• BuildMode = "build" is a valid value (bent.go:68 validateBuildMode); it builds a main package, so the repo retarget from library packages (.../cl, .../ixgo) to cmd/xgo / cmd/ixgo is required and correct.
• It mirrors the existing etcdctl precedent (suites.toml:236-239).
• Versions stay pinned to explicit tags (@v1.7.5, @v1.1.1), consistent with the rest of the file; no shell-injection or trust-boundary surface is introduced.

No correctness, security, or performance issues in the diff itself.

Findings

1. Doc now understates build-mode scope — ci/llgo-size/README.md:19-20 (not in this diff)

The README states the build-mode path applies only to etcdctl:

The etcdctl case sets BuildMode = "build" and exercises the new go build / llgo build path...

After this PR, XGo and iXGo also set BuildMode = "build" and are main-package builds. The same README already lists all three suites together (line 13). Consider updating lines 19-21 to note that XGo and iXGo are now build-mode cases too, so the doc matches the config.

2. Behavioral note (no change needed): per cmd/bent/README.md:97, Bent does not execute build-mode binaries during the run phase. Switching XGo/iXGo to build means these suites now measure build/binary output only and no longer execute at runtime. This appears intentional (matches etcdctl and the llgo-size configs), but is a change in what is measured — worth confirming any downstream dashboards expecting run-phase numbers for these suites.