fatal: iconv_open(UTF-8,UTF-8-MAC) failed, but needed:

Sometimes when using git commands I get this error:

```
fatal: iconv_open(UTF-8,UTF-8-MAC) failed, but needed:
precomposed unicode is not supported.
If you want to use decomposed unicode, run
"git config core.precomposeunicode false"
```

The error does not occur with other builds of git. I even built the same version of git from source and didn't have the issue.

This is on the osx build.

No files or tests are named. Start by reproducing the iconv_open error with the OSX build, then compare that build with the working source and other Git builds described in the issue. Done means the build-specific cause is identified and the error is resolved or the required configuration is documented.

Written by the indexing model from the issue text.