build fails on rustc-1.30-stable

[kod-kristoff]

error[E0554]: #![feature] may not be used on the stable release channel
   --> /data/data/com.termux/files/home/.cargo/registry/src/github.com-1ecc6299db9ec823/regex-0.2.11/src/lib.rs:522:34                                       |
522 | #![cfg_attr(feature = "pattern", feature(pattern))]
    |                                  ^^^^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0554`.
error: Could not compile `regex`.                  warning: build failed, waiting for other jobs to finish...                                            
error: build failed

I have tried cargo update but the build still fails.

[kod-kristoff]

updating regex to version 1.0.6 helps, but the build still fails:

cargo build                                          
   Updating crates.io index
   Compiling regex v1.0.6                               
   Compiling regex-syntax v0.6.3
   Compiling fuel_line_derive v0.1.0        
error[E0554]: #![feature] may not be used on the stable release channel                                --> /data/data/com.termux/files/home/.cargo/registry/src/github.com-1ecc6299db9ec823/fuel_line_derive-0.1.0/src/lib.rs:1:1
  |                                                1 | 
#![feature(proc_macro)]
  | ^^^^^^^^^^^^^^^^^^^^^^^                        
error: aborting due to previous error              
For more information about this error, try `rustc --explain E0554`.
error: Could not compile `fuel_line_derive`.       warning: build failed, waiting for other jobs to finish...                                            
error: build failed

So this is an upstream problem.