Rust 1.50.0 pre-release testing

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I am reproducibly seeing the following failure from x.py build against the 1.50.0 source dist in my work environment (where we've built just about every release since 1.11.0 successfully). It fails at rust/lib.rs at 690501e3e9535389a1441cee74d049ba16b963fa · rust-lang/rust · GitHub after "Assembling stage1 compiler". Still investigating but I figured I'd raise it in case anyone is seeing the same.

Assembling stage1 compiler (x86_64-unknown-linux-gnu)
thread 'main' panicked at 'src.symlink_metadata() failed with No such file or directory (os error 2)', src/bootstrap/lib.rs:1192:24
stack backtrace:
   0: rust_begin_unwind
             at /rustc/e1884a8e3c3e813aada8254edfa120e85bf5ffca/library/std/src/panicking.rs:495:5
   1: std::panicking::begin_panic_fmt
             at /rustc/e1884a8e3c3e813aada8254edfa120e85bf5ffca/library/std/src/panicking.rs:437:5
   2: bootstrap::Build::copy
             at ./rust/src/bootstrap/lib.rs:1192:24
   3: <bootstrap::compile::Assemble as bootstrap::builder::Step>::run
             at ./rust/src/bootstrap/compile.rs:1025:13
   4: bootstrap::builder::Builder::ensure
             at ./rust/src/bootstrap/builder.rs:1488:23
   5: bootstrap::builder::Builder::compiler
             at ./rust/src/bootstrap/builder.rs:579:9
   6: <bootstrap::compile::Std as bootstrap::builder::Step>::make_run
             at ./rust/src/bootstrap/compile.rs:48:23
   7: bootstrap::builder::StepDescription::maybe_run
             at ./rust/src/bootstrap/builder.rs:179:13
   8: bootstrap::builder::StepDescription::run
             at ./rust/src/bootstrap/builder.rs:200:25
   9: bootstrap::builder::Builder::run_step_descriptions
             at ./rust/src/bootstrap/builder.rs:571:9
  10: bootstrap::builder::Builder::execute_cli
             at ./rust/src/bootstrap/builder.rs:562:9
  11: bootstrap::Build::build
             at ./rust/src/bootstrap/lib.rs:510:13
  12: bootstrap::main
             at ./rust/src/bootstrap/bin/main.rs:30:5

Full output: https://paste.rs/qzm