Building latest release for Windows on Ubuntu 16.04 fails unless --disable-rust is specified

[PeaStew]

Describe the issue

Building latest release (2001051) for Windows on Ubuntu 16.04 fails unless --disable-rust is specified Error is "~/../zen/depends/x86_64-w64-mingw32/share/../lib/librustzcash.a(rustzcash-4f7569c7f76c9f1d.0.o): could not read symbols: Invalid operation".

Builds fine if --disable-rust is specified, but this is not mentioned in build instructions.

May be related to: https://github.com/z-classic/zclassic/issues/69

Can you reliably reproduce the issue?

If so, please list the steps to reproduce below:

1. Install all required build tools as specified in howto
2. Build for windows with "./zcutil/build-win.sh -j$(nproc)"

Expected behaviour

Build should succeed.

Actual behaviour + errors

Build fails with "~/../zen/depends/x86_64-w64-mingw32/share/../lib/librustzcash.a(rustzcash-4f7569c7f76c9f1d.0.o): could not read symbols: Invalid operation".

The version of Zen you were using:

Trying to build 2001051

Machine specs:

• OS name + version: Ubuntu 16.04 LTS
• CPU: Intel(R) Atom(TM) CPU C2750 @ 2.40GHz
• RAM: 8GB
• Disk size: 128GB
• Disk Type (HD/SDD): SSD
• Linux kernel version (uname -a): 4.4.0-101-generic #124-Ubuntu SMP Fri Nov 10 18:29:59 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
• Compiler version (gcc -version): 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.5)

Any extra information that might be useful in the debugging process.

N/A

Do you have a back up of ~/.zen directory and/or take a VM snapshot?

N/A

[PeaStew]

If there is no librustzcash for windows then the build instructions could just be changed to have --disable-rust as the ARM instructions do. Probably relevant (according to other issue) for OSX instructions also.

[cronicc]

Build instructions were updated.