Spurious failures on AppVeyor due to ar.exe errors #40546
Description
I've previously been classifying these errors under #40240 but now I'm thinking that's incorrect, I suspect these are totally separate errors.
https://ci.appveyor.com/project/rust-lang/rust/build/1.0.2397
[ 13%] Linking CXX static library ../../libLLVMMCDisassembler.a C:/projects/rust/mingw64/bin/ar.exe: ../../libLLVMMCDisassembler.a: Permission denied make[2]: *** [lib/MC/MCDisassembler/CMakeFiles/LLVMMCDisassembler.dir/build.make:205: lib/libLLVMMCDisassembler.a] Error 1 make[2]: *** Deleting file 'lib/libLLVMMCDisassembler.a' make[1]: *** [CMakeFiles/Makefile2:2539: lib/MC/MCDisassembler/CMakeFiles/LLVMMCDisassembler.dir/all] Error 2 make[1]: *** Waiting for unfinished jobs.... [ 13%] Built target LLVMMCParser make: *** [Makefile:150: all] Error 2 thread 'main' panicked at ' command did not execute successfully, got: exit code: 2