File meson.build of Package failed_boxfort

```meson
project('boxfort', 'c',
  version: '0.0.1',
  default_options: ['warning_level=3'])

# Check for supported architectures
supported_archs = ['x86_64', 'aarch64', 'arm', 'ppc64le', 's390x', 'riscv64']

host_arch = host_machine.cpu_family()
if not supported_archs.contains(host_arch)
  error('Architecture "@0@" is not supported.'.format(host_arch))
endif

# Compiler flags
add_project_arguments('-Wall', '-Wno-unused-parameter', '-Wno-unused-value', '-fvisibility=hidden', language: 'c')

# Dependencies
threads = dependency('threads')
rt = cc.find_library('rt', required: true)
m = cc.find_library('m', required: true)

# Sources
sources = files(
  'src/main.c',
  'src/utils.c',
)

# Executable
executable('boxfort',
  sources,
  dependencies: [threads, rt, m],
  install: true,
)
```

### Explanation of Changes:
1. **Added `riscv64` to `supported_archs`:**
   - The `supported_archs` array was updated to include `'riscv64'` alongside other supported architectures like `'x86_64'`, `'aarch64'`, etc.
   - This ensures that the build system recognizes `riscv64` as a valid architecture.

2. **No Other Changes Made:**
   - The rest of the file remains unchanged to adhere to the principle of minimal edits.

### Next Steps:
- Replace the existing `meson.build` file in the package directory with the updated content provided above.
- Re-run the build process to verify that the issue is resolved.