Spurious `gdb failed to execute` on Windows

[arielb1]

First seen in #41840 - https://ci.appveyor.com/project/rust-lang/rust/build/1.0.3595/job/4s8ofgv42um1t8b2:

failures:
---- [debuginfo-gdb] debuginfo-gdb\borrowed-c-style-enum.rs stdout ----
	NOTE: compiletest thinks it is using GDB without native rust support
NOTE: compiletest thinks it is using GDB version 7010001
error: gdb failed to execute
thread '[debuginfo-gdb] debuginfo-gdb\borrowed-c-style-enum.rs' panicked at 'explicit panic', src\tools\compiletest\src\runtest.rs:1651

[kennytm]

The error code from #44261 is 1816, which is ERROR_NOT_ENOUGH_QUOTA (Not enough quota is available to process this command.)