The lost boy somehow kept it together until the rescue team arrived.
Literal
Lost-child [possessive-の] boy [topic-は] rescue-team [subject-が] come [until-まで] somehow hung-on.
迷子 ('lost child') is a fixed compound. ~まで with a verb clause gives the temporal 'until X happens' frame. 何とか ('somehow, in some way or another') suggests a difficult struggle — he managed it with effort, not easily. 頑張る ('do one's best, hold on') is the famously ubiquitous Japanese verb for perseverance.