ChangXin Memory Technologies is approaching a turning point.The Chinese memory-chip maker has advanced far enough to draw interest from some of the world's largest technology companies, including Apple Inc., which has considered using its chips. But the same growth that has raised CXMT's commercial standing has also made it a more prominent target in the widening technology confrontation between Washington and Beijing.The Pentagon has blacklisted the state-backed company over alleged links to China's military. In South Korea, prosecutors have accused several former Samsung Electronics employees of leaking proprietary information to CXMT. The company's expansion is also being watched closely by…