$ ./mach build
 0:00.68 Clobber not needed.
 Config object not found by mach.
created virtual environment CPython3.7.9.final.0-64 in 236ms
  creator CPython3Windows(dest=C:\dev\mozilla-central\obj-x86_64-pc-mingw32\_virtualenvs\build, clear=False, no_vcs_ignore=False, global=False)
  activators BashActivator,BatchActivator,FishActivator,PowerShellActivator,PythonActivator
 0:01.40 c:/dev/mozilla-central/obj-x86_64-pc-mingw32\_virtualenvs\build\Scripts\python.exe c:/dev/mozilla-central\configure.py
 0:01.60 Using Python 3.7.9 from c:\dev\mozilla-central\obj-x86_64-pc-mingw32\_virtualenvs\build\Scripts\python.exe
 0:01.62 checking for vcs source checkout... hg
 0:01.67 checking for a shell... C:/mozilla-build/msys/bin/sh.exe
 0:01.67 checking for host system type... x86_64-pc-mingw32
 0:01.67 checking for target system type... x86_64-pc-mingw32
 0:02.10 checking whether cross compiling... no
 0:02.27 checking for Python 3... c:/dev/mozilla-central/obj-x86_64-pc-mingw32/_virtualenvs/build/Scripts/python.exe (3.7.9)
 0:02.27 checking for hg... c:/mozilla-build/python/Scripts/hg.exe
 0:02.38 checking for Mercurial version... 5.9.3+hg10.266e1f0338f9
 0:02.53 checking for sparse checkout... no
 0:10.57 checking for wget... c:/mozilla-build/bin/wget.exe
 0:10.60 checking for ccache... not found
 0:10.60 checking for the target C compiler... c:/Users/Developer/.mozbuild/clang/bin/clang-cl.exe
 0:10.66 checking whether the target C compiler can be used... yes
 0:10.66 checking the target C compiler version... 13.0.0
 0:10.69 checking the target C compiler works... yes
 0:10.69 checking for the target C++ compiler... c:/Users/Developer/.mozbuild/clang/bin/clang-cl.exe
 0:10.75 checking whether the target C++ compiler can be used... yes
 0:10.75 checking the target C++ compiler version... 13.0.0
 0:10.78 checking the target C++ compiler works... yes
 0:10.78 checking for the host C compiler... c:/Users/Developer/.mozbuild/clang/bin/clang-cl.exe
 0:10.84 checking whether the host C compiler can be used... yes
 0:10.84 checking the host C compiler version... 13.0.0
 0:10.87 checking the host C compiler works... yes
 0:10.87 checking for the host C++ compiler... c:/Users/Developer/.mozbuild/clang/bin/clang-cl.exe
 0:10.93 checking whether the host C++ compiler can be used... yes
 0:10.93 checking the host C++ compiler version... 13.0.0
 0:10.96 checking the host C++ compiler works... yes
 0:11.00 checking for 64-bit OS... yes
 0:11.04 checking for Windows SDK... 0x0a00 in C:/PROGRA~2/WI3CF2~1/10/
 0:11.04 checking for Universal CRT SDK... 10.0.20348.0 in C:/PROGRA~2/WI3CF2~1/10/
 0:11.04 checking for linker... c:/Users/Developer/.mozbuild/clang/bin/lld-link.exe
 0:11.04 checking for host_linker... c:/Users/Developer/.mozbuild/clang/bin/lld-link.exe
 0:11.04 checking for the assembler... C:/PROGRA~2/MICROS~4/2019/COMMUN~1/VC/Tools/MSVC/1429~1.301/bin/HostX64/x64/ml64.exe
 0:11.04 checking for rc... c:/Users/Developer/.mozbuild/clang/bin/llvm-rc.exe
 0:11.04 checking for ar... c:/Users/Developer/.mozbuild/clang/bin/llvm-lib.exe
 0:11.08 checking for stdint.h... yes
 0:11.12 checking for inttypes.h... yes
 0:11.16 checking for malloc.h... yes
 0:11.19 checking for alloca.h... no
 0:11.23 checking for sys/byteorder.h... no
 0:11.26 checking for getopt.h... no
 0:11.29 checking for unistd.h... no
 0:11.32 checking for nl_types.h... no
 0:11.36 checking for cpuid.h... yes
 0:11.39 checking for fts.h... no
 0:11.42 checking for sys/statvfs.h... no
 0:11.45 checking for sys/statfs.h... no
 0:11.49 checking for sys/vfs.h... no
 0:11.52 checking for sys/mount.h... no
 0:11.55 checking for sys/quota.h... no
 0:11.58 checking for sys/queue.h... no
 0:11.62 checking for sys/types.h... yes
 0:11.65 checking for netinet/in.h... no
 0:11.68 checking for byteswap.h... no
 0:11.71 checking for memfd_create in sys/mman.h... no
 0:11.75 checking for perf_event_open system call... no
 0:11.76 checking for llvm_profdata... c:/Users/Developer/.mozbuild/clang/bin/llvm-profdata.exe
 0:11.77 checking for rustc... c:/Users/Developer/.cargo/bin/rustc.exe
 0:11.77 checking for cargo... c:/Users/Developer/.cargo/bin/cargo.exe
 0:11.91 Actually using 'C:\Users\Developer\.rustup\toolchains\stable-x86_64-pc-windows-msvc\bin\rustc.exe'
 0:12.04 Actually using 'C:\Users\Developer\.rustup\toolchains\stable-x86_64-pc-windows-msvc\bin\cargo.exe'
 0:12.06 checking rustc version... 1.49.0
 0:12.07 checking cargo version... 1.49.0
 0:12.07 ERROR: Rust compiler 1.49.0 is too old.
 0:12.07 To compile Rust language sources please install at least
 0:12.07 version 1.57.0 of the 'rustc' toolchain (or, if using nightly,
 0:12.07 at least one version newer than 1.57.0) and make sure it is
 0:12.07 first in your path.
 0:12.07 You can verify this by typing 'rustc --version'.
 0:12.07 If you have the 'rustup' tool installed you can upgrade
 0:12.07 to the latest release by typing 'rustup update'. The
 0:12.08 installer is available from https://rustup.rs/
Error running mach:

    ['build']

The error occurred in code that was called by the mach command. This is either
a bug in the called code itself or in the way that mach is calling it.
You can invoke |./mach busted| to check if this issue is already on file. If it
isn't, please use |./mach busted file build| to report it. If |./mach busted| is
misbehaving, you can also inspect the dependencies of bug 1543241.

If filing a bug, please include the full output of mach, including this error
message.

The details of the failure are as follows:

Exception: Process executed with non-0 exit code 1: ['c:/dev/mozilla-central/obj-x86_64-pc-mingw32\\_virtualenvs\\build\\Scripts\\python.exe', 'c:/dev/mozilla-central\\configure.py']

  File "c:\dev\mozilla-central\python/mozbuild/mozbuild/build_commands.py", line 229, in build
    append_env=append_env,
  File "c:\dev\mozilla-central\python\mozbuild\mozbuild\controller\building.py", line 1300, in build
    append_env=append_env,
  File "c:\dev\mozilla-central\python\mozbuild\mozbuild\controller\building.py", line 1680, in configure
    append_env=append_env,
  File "c:\dev\mozilla-central\python\mozbuild\mozbuild\base.py", line 857, in _run_command_in_objdir
    return self.run_process(cwd=self.topobjdir, **args)
  File "c:\dev\mozilla-central\python\mach\mach\mixin\process.py", line 181, in run_process
    "Process executed with non-0 exit code %d: %s" % (status, args)