fix(hermes): pick static_h vs main branch by RCT_HERMES_V1_ENABLED in hermes-utils.rb

[Thiago Vinhas (tvinhas)]

Summary

Companion to #2952 (JS-side / microsoft-hermes.js). That PR switches the producer-side hermesCommitAtMergeBase() in JS from main → static_h when resolving Hermes V1; this PR applies the same logic to the consumer-side Ruby
equivalent in hermes-utils.rb.

Before:

gitclone -q --bare --filter=blob:none --single-branch --branchmain#{HERMES_GITHUB_URL} ...commit=`git --git-dir=... rev-list -1 --before=#{timestamp} refs/heads/main`.stripAfter:
hermes_branch=hermes_v1_enabled() ? "static_h" : "main"gitclone ... --branch#{hermes_branch} ...commit=`git --git-dir=... rev-list -1 --before=#{timestamp} refs/heads/#{hermes_branch}`.stripWhyitmattersThehermes_commit_at_merge_baseRubyfunctionisthefrom-sourcefallbackpath: itfireswhenneithertheV0norV1MaventarballisavailableANDRCT_BUILD_HERMES_FROM_SOURCE=true.Withthehardcodedmainbranch,RCT_HERMES_V1_ENABLED=1
+ from-sourcebuildwouldcloneV0HermessourcewhiletherestofthepodspecexpectstheV1hermesvm.framework / hermesvm.xcframeworkartifacts—asilentmismatchthatfailslateinthebuildwithconfusing"missing framework"errors.Afterthischangethebranchmatchestheenginevarianttherestofthepodspecresolvesat.Partiallyclosesthe"Hermes V1 support"itemontheRoadto0.83trackingissue(#2901) — together with #2952 (CI / JS side), the producer + consumer Ruby/JS sides are aligned. The other Hermes-V1 plumbing in hermes-engine.podspec,version.properties,and.hermesv1versionwasalreadybroughtinbytheupstream0.83merge.TestPlan
- Defaultpath(RCT_HERMES_V1_ENABLED=0,legacyV0): hermes_branchresolvesto"main",behaviorunchanged.Verifiedbyreadingthediff—onlythevariablesubstitutiondiffersfromtheprevioushardcodedpath.
- V1path(RCT_HERMES_V1_ENABLED=1): hermes_branchresolvesto"static_h",matching#2952's JS-side selection and matching the actual upstream Hermes branch that hosts the V1 (0.83+) source.
- podinstallinpackages/rn-testeron0.83-mergesucceedswith86deps / 85installed(validatedlocally;thispathisdormantonthecache-hit / Maven-tarball-availablepathsbutexercisingitmanuallywithV1 + from-sourceproducestheexpectedhermesvm.xcframeworkshape).
- Rubysyntaxcheck(ruby -c): clean.Related
- #2952 — CI / JS-side companion fix (still draft as of writing)
- #2901 — Road to 0.83 tracking issue (partial close)