Spurious WebRender failure: 'gperf' is missing on your system

[emilyalbini]

Occasionally the x86_64-gnu-aux builder fails due to a spurious build failure:

make[2]: warning: -jN forced in submake: disabling jobserver mode.
/cargo/registry/src/github.com-1ecc6299db9ec823/servo-fontconfig-sys-4.0.4/missing: line 81: gperf: command not found
WARNING: 'gperf' is missing on your system.
         You might have modified some files without having the proper
         tools for further handling them.  Check the 'README' file, it
         often tells you about the needed prerequisites for installing
         this package.  You may also peek at any GNU archive site, in
         case some other package contains this missing 'gperf' program.
make[4]: *** [fcobjshash.h] Error 1
make[4]: *** Waiting for unfinished jobs....
make[3]: *** [all-recursive] Error 1
make[2]: *** [all] Error 2
make[1]: *** [/checkout/obj/build/ct/webrender/target/debug/build/servo-fontconfig-sys-e3947402e30e86b7/out/libfontconfig.a] Error 2
thread 'main' panicked at 'assertion failed: Command::new("make").env("MAKEFLAGS",
                         env::var("CARGO_MAKEFLAGS").unwrap_or_default()).args(&["-R",
                                                                                 "-f",
                                                                                 "makefile.cargo"]).status().unwrap().success()', /cargo/registry/src/github.com-1ecc6299db9ec823/servo-fontconfig-sys-4.0.4/build.rs:17:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

The WebRender people prepared a fix, but it did not land in https://github.com/servo/webrender yet. Once it lands, we'll need to update cargotest to point to the new commit.

Putting it P-high so we check in on it weekly during the infrastructure team meeting.

[emilyalbini]

Discussed this at the infra meeting, there is a PR removing webrender. De-prioritizing.