Rollup merge of #34558 - GlenDC:master, r=alexcrichton
Rollup merge of #34558 - GlenDC:master, r=alexcrichton

rustbuild: propagate bootstrap.py '--help' flag

Fixes #34534.
r? @alexcrichton

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