Rust build fails

[Martin Husemann <martin%duskware.de@localhost>]

Trying to build rust on NetBSD/sparc64 -current fails:

===> Creating toolchain wrappers for rust-1.49.0
===> Configuring for rust-1.49.0
=> Substituting "cksum" in vendor/libc/.cargo-checksum.json vendor/lzma-sys/.cargo-checksum.json vendor/stacker/.cargo-checksum.json vendor/net2/.cargo-checksum.json vendor/openssl-src/.cargo-checksum.json
=> Substituting "rpath" in compiler/rustc_codegen_ssa/src/back/linker.rs compiler/rustc_target/src/spec/netbsd_base.rs src/bootstrap/builder.rs src/bootstrap/compile.rs
=> Checking for portability problems in extracted files
configure: processing command line
configure: 
configure: install.prefix       := /usr/pkg
configure: install.mandir       := /usr/pkg/man
configure: install.sysconfdir   := /usr/pkg/etc
configure: build.python         := /usr/pkg/bin/python3.8
configure: rust.channel         := stable
configure: build.rustc          := /usr/pkgobj/lang/rust/work/rust-bootstrap/bin/ ...
configure: build.cargo          := /usr/pkgobj/lang/rust/work/rust-bootstrap/bin/ ...
configure: build.extended       := True
configure: rust.rpath           := True
configure: rust.codegen-tests   := False
configure: rust.dist-src        := False
configure: llvm.static-libstdcpp := False
configure: llvm.ninja           := False
configure: build.vendor         := True
configure: llvm.link-shared     := True
configure: target.sparc64-unknown-netbsd.llvm-config := /usr/pkg/bin/llvm-config
configure: build.configure-args := ['--prefix=/usr/pkg', '--mandir=/usr/pkg/man', ...
configure: 
configure: writing `config.toml` in current directory
configure: 
configure: run `python /usr/pkgobj/lang/rust/work/rustc-1.49.0-src/x.py --help`
configure: 
=> Modifying libtool scripts to use pkgsrc libtool
=> Modifying libtool scripts to use pkgsrc depcomp
===> Building for rust-1.49.0
rustup not detected: [Errno 2] No such file or directory: 'rustc'
falling back to auto-detect
rustup not detected: [Errno 2] No such file or directory: 'rustc'
falling back to auto-detect
running: /usr/pkgobj/lang/rust/work/rust-bootstrap/bin/cargo build --manifest-path /usr/pkgobj/lang/rust/work/rustc-1.49.0-src/src/bootstrap/Cargo.toml --frozen
Traceback (most recent call last):
  File "./x.py", line 11, in <module>
    bootstrap.main()
  File "/usr/pkgobj/lang/rust/work/rustc-1.49.0-src/src/bootstrap/bootstrap.py", line 1089, in main
    bootstrap(help_triggered)
  File "/usr/pkgobj/lang/rust/work/rustc-1.49.0-src/src/bootstrap/bootstrap.py", line 1062, in bootstrap
    build.build_bootstrap()
  File "/usr/pkgobj/lang/rust/work/rustc-1.49.0-src/src/bootstrap/bootstrap.py", line 829, in build_bootstrap
    run(args, env=env, verbose=self.verbose)
  File "/usr/pkgobj/lang/rust/work/rustc-1.49.0-src/src/bootstrap/bootstrap.py", line 153, in run
    raise RuntimeError(err)
RuntimeError: failed to run: /usr/pkgobj/lang/rust/work/rust-bootstrap/bin/cargo build --manifest-path /usr/pkgobj/lang/rust/work/rustc-1.49.0-src/src/bootstrap/Cargo.toml --frozen
*** Error code 1

Stop.
make[8]: stopped in /usr/pkgsrc/lang/rust


Any hints?

Martin