There is parallelism here which we must take into account. With parallelism, it's not always clear whether equating the two parallel concepts is intended by the author or not, and is largely a subjective endeavor, however, I think this case is quite clear:
Are you the first man that was born | or | were you made before the hills?
Have thou heard God's counsel | and | shall you take away wisdom to yourself?
Since Proverbs, also Wisdom Literature, written after Job and based on the same idea of personifying God's wisdom, says the following:
I, wisdom ... ... The mountains with their huge bulk had not as yet been established: before the hills I was brought forth:
This seems to be quite an overt allusion to this passage. However, wisdom is not a "man born," but a personification of God's wisdom. It seems to be the case, therefore, that Job 15:7a and Job 15:7b might not be equating "the first man" with being "made before the hills," as this is not a necessary link. It's more likely two successive examples of being of prime importance: the first manever born; 'God thought it essential to make you, even before getting around to making the mountains' (accusing Job or pride, or mocking his futility).