swallowed output line visible only upon second compile invocation

[ghost]

While encountering this issue, I've noticed a discrepancy in the ouput while compiling Rust:
The compile error was referencing rustc_driver but the previous output contained no line(within a decent range from the error) saying Compiling rustc_driver v0.0.0, as if that line was somehow lost due to some kind of output buffer not being flushed, or something.

I expected to see this happen:

Compiling rustc_passes v0.0.0 (file:///home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/src/librustc_passes)
Compiling rustc_driver v0.0.0 (file:///home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/src/librustc_driver)
fragment covers entire variable

Instead, this happened:

Compiling rustc_passes v0.0.0 (file:///home/xftroxgpx/build/2nonpkgs/rust.stuff/rust/rust/src/librustc_passes)
fragment covers entire variable

Now, there is one Compiling rustc_driver line here however that line is so far from the compile error that it doesn't seem to make any sense that that line is then the first and only line on the subsequent compilation attempt.

In other words:

Why is the line with Compiling rustc_driver missing in the first compilation attempt here:
https://gist.github.com/xftroxgpx/5eef3141eab2e4ccdfe0fa3255ff921d/d05bc152c4c4c02c4e241a60a278a940bb0549db#file-console-rs-L5015-L5018

but it's there in the second compilation attempt:
https://gist.github.com/xftroxgpx/5eef3141eab2e4ccdfe0fa3255ff921d/d05bc152c4c4c02c4e241a60a278a940bb0549db#file-console-rs-L5069-L5072

I even tried the above for a second time:

• missing on first time compilation:
  https://gist.github.com/xftroxgpx/5eef3141eab2e4ccdfe0fa3255ff921d/212fababd444b3caa8cfde7971a6e79867c61383#file-console-rs-L4996-L4999

• visible on second time compilation:
  https://gist.github.com/xftroxgpx/5eef3141eab2e4ccdfe0fa3255ff921d/212fababd444b3caa8cfde7971a6e79867c61383#file-console-rs-L5049-L5052

rustc used to compile (probably)

$ ~/.cargo/bin/rustc -vV
rustc 1.26.0-nightly (2789b067d 2018-03-06)
binary: rustc
commit-hash: 2789b067da2ac921b86199bde21dd231ace1da39
commit-date: 2018-03-06
host: x86_64-unknown-linux-gnu
release: 1.26.0-nightly
LLVM version: 6.0

[jyn514]

Duplicate of rust-lang/cargo#8889