Fails to build if a user does not have rustup dependency

[smailbarkouch]

Error (from @Parth )

Cloning into 'lockbook'...
done.
==> Starting pkgver()...
==> Sources are ready.
==> Making package: lockbook-desktop 0.4.1-3 (Tue 07 Jun 2022 01:20:18 PM EDT)
==> Checking runtime dependencies...
==> Checking buildtime dependencies...
==> WARNING: Using existing $srcdir/ tree
==> Starting pkgver()...
==> Starting build()...
lockbook-desktop
/home/parth/.cache/yay/lockbook-desktop/PKGBUILD: line 25: rustup: command not found
==> ERROR: A failure occurred in build().
    Aborting...
 -> error making: lockbook-desktop

A simple fix should be replacing the rust make dependency with rustup.