Auto merge of #8403 - matklad:abs-out-dir, r=Eh2406
Auto merge of #8403 - matklad:abs-out-dir, r=Eh2406

Document that OUT_DIR in JSON messages is an absolute path

tshepang/cargo,eminence/cargo,rust-lang/cargo,eminence/cargo,nipunn1313/cargo,tshepang/cargo,rustyhorde/cargo,eminence/cargo,rust-lang/cargo,rustyhorde/cargo,tsurai/cargo,tshepang/cargo,rustyhorde/cargo,tshepang/cargo,nipunn1313/cargo,tsurai/cargo,rust-lang/cargo,tsurai/cargo,rustyhorde/cargo,nipunn1313/cargo,eminence/cargo,tsurai/cargo,tsurai/cargo,nipunn1313/cargo,rust-lang/cargo