Auto merge of #27221 - dotdash:no_empty_clean, r=luqmana
Auto merge of #27221 - dotdash:no_empty_clean, r=luqmana

When compiling libsyntax this removes about 30k basic blocks that only
contain a single unconditional jump and reduces the peak memory usage by
about 10MB (from 681MB down to 671MB).

jashank/rust,vhbit/rust,jashank/rust,GBGamer/rust,pshc/rust,aidancully/rust,jashank/rust,graydon/rust,GBGamer/rust,graydon/rust,zubron/rust,zubron/rust,vhbit/rust,aidancully/rust,pshc/rust,GBGamer/rust,jroesch/rust,aidancully/rust,GBGamer/rust,jroesch/rust,l0kod/rust,l0kod/rust,dwillmer/rust,jroesch/rust,GBGamer/rust,vhbit/rust,pshc/rust,l0kod/rust,jroesch/rust,dwillmer/rust,vhbit/rust,pshc/rust,GBGamer/rust,zubron/rust,aidancully/rust,jashank/rust,dwillmer/rust,pshc/rust,l0kod/rust,jashank/rust,graydon/rust,jashank/rust,zubron/rust,graydon/rust,jroesch/rust,zubron/rust,vhbit/rust,aidancully/rust,jroesch/rust,l0kod/rust,dwillmer/rust,dwillmer/rust,jroesch/rust,graydon/rust,vhbit/rust,jroesch/rust,jashank/rust,zubron/rust,dwillmer/rust,pshc/rust,dwillmer/rust,GBGamer/rust,pshc/rust,graydon/rust,l0kod/rust,aidancully/rust,pshc/rust,vhbit/rust,zubron/rust,l0kod/rust,l0kod/rust,vhbit/rust,zubron/rust,dwillmer/rust,jashank/rust,GBGamer/rust