librustc_trans: Turn PGO diagnostics into warnings.
librustc_trans: Turn PGO diagnostics into warnings.

They should at least be that, they usually warn about control flow mismatches,
and or the profile being useless, which looks like at least a warning to me.

Signed-off-by: Emilio Cobos Álvarez <86fa523305b8ad6a8a853c04cfef24a0445908d3@crisal.io>

graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust