Dear maintainers,

Compiling the justbuild failed for loong64 in the Debian Package
Auto-Building environment.
The error log is as follows,
```
In file included from work/src/buildtool/file_system/atomic.cpp:15:
work/src/buildtool/file_system/atomic.hpp:18:10: fatal error: 'string'
file not found
    18 | #include <string>
       |          ^~~~~~~~
1 error generated.
......
subprocess.CalledProcessError: Command '['clang++', '-target',
'x86_64-linux-gnu', '-O2', '-DNDEBUG', '-Wall', '-Wextra', '-Wpedantic',
'-Wsign-conversion', ......
```
The full build log can be found at
https://buildd.debian.org/status/fetch.php?pkg=justbuild&arch=loong64&ver=1.5.1-1&stamp=1745330600&raw=0.

Please consider the patch I attached.
Based on the attached patch, justbuild was built successfully on locally.
Please note that the dependency libprotobuf-dev of justbuild lacks
loongarch64 support(I have submitted bug and patch to protobuf source
package, too).
```
......
    dh_builddeb
dpkg-deb: building package 'justbuild' in
'../justbuild_1.5.1-1+loong64_loong64.deb'.
dpkg-deb: building package 'justbuild-dbgsym' in
'../justbuild-dbgsym_1.5.1-1+loong64_loong64.deb'.
  dpkg-genbuildinfo --build=binary
-O../justbuild_1.5.1-1+loong64_loong64.buildinfo
  dpkg-genchanges --build=binary
-O../justbuild_1.5.1-1+loong64_loong64.changes
```

Please add loongarch64 support in the next upload.
Your opinions are welcome.

Best regards,
Dandan Zhang