ci: include public credentials in the linuxtools pr job
ci: include public credentials in the linuxtools pr job

This allows the use of sccache to compile LLVM, and should fix toolstate
not working.

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