Auto merge of #28691 - utkarshkukreti:add-path_max-to-liblibc, r=alexcrichton
Auto merge of #28691 - utkarshkukreti:add-path_max-to-liblibc, r=alexcrichton

PATH_MAX is defined for OSX and various BSDs but not Linux right now.

[Source for the value.](https://github.com/torvalds/linux/blob/9ffecb10283508260936b96022d4ee43a7798b4c/include/uapi/linux/limits.h#L12)

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