This allows libmono to load extra libraries (notably win-iconv) from
system_dllpath.
For example, Fedora's wine-mono is built against a shared win-iconv
installed in system_dllpath, but wine will not search there unless it's
explicitly instructed to do so since bfbccf1a038e (ntdll: Prevent
loading Wine system dependencies in place of identically named application
DLLs.).
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54573
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https://gitlab.winehq.org/wine/wine/-/merge_requests/7077