Rollup merge of #32212 - Manishearth:ice-cu, r=eddyb
Rollup merge of #32212 - Manishearth:ice-cu, r=eddyb

Don't allow values for codegen-units less than 1

r? @eddyb

fixes #32191

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