Can't build on Manjaro/Arch Linux: No vcpkg installation found.

[HaleTom]

In building rustdesk, I come across this error:

   Compiling scrap v0.5.0 (/home/var/ravi/.cache/aur/rustdesk/src/rustdesk-1.1.9/libs/scrap)
   Compiling magnum-opus v0.4.0 (https://github.com/open-trade/magnum-opus#3c3d0b86)
error: failed to run custom build command for `scrap v0.5.0 (/home/var/ravi/.cache/aur/rustdesk/src/rustdesk-1.1.9/libs/scrap)`

Caused by:
  process didn't exit successfully: `/home/var/ravi/.cache/aur/rustdesk/src/rustdesk-1.1.9/target/release/build/scrap-2136fd8803e9c6e2/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'Failed to find package: VcpkgNotFound("No vcpkg installation found. Set the VCPKG_ROOT environment variable or run 'vcpkg integrate install'")', libs/scrap/build.rs:7:45
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
error: could not find native static library `opus`, perhaps an -L flag is missing?

error: could not compile `magnum-opus` due to previous error
==> ERROR: A failure occurred in build().

So what value for VCPKG_ROOT?

% cat /usr/bin/vcpkg
#!/bin/sh
export VCPKG_ROOT=/opt/vcpkg
export VCPKG_DOWNLOADS=/var/cache/vcpkg

$VCPKG_ROOT/vcpkg "$@"

So after manually:

export VCPKG_ROOT=/opt/vcpkg
export VCPKG_DOWNLOADS=/var/cache/vcpkg

The output changes to:

   Compiling scrap v0.5.0 (/home/var/ravi/.cache/aur/rustdesk/src/rustdesk-1.1.9/libs/scrap)

Caused by:
  process didn't exit successfully: `/home/var/ravi/.cache/aur/rustdesk/src/rustdesk-1.1.9/target/release/build/scrap-2136fd8803e9c6e2/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'Failed to find package: VcpkgInstallation("could not read status file updates dir: No such file or directory (os error 2)")', libs/scrap/build.rs:7:45

About 430 modules of rustdesk have build just fine so far, so I'm wondering if there is something special going on with scrap?