pocheck: fix usage message

pocheck needs environment variables that bin/run does not provide

Change-Id: I0de148363d60c515d4024cd0e97d1025ce50b6a5
Reviewed-on: https://gerrit.libreoffice.org/61160
Tested-by: Jenkins
Reviewed-by: Andras Timar <andras.timar@collabora.com>

l10ntools/source/pocheck.cxx

@@ -458,7 +458,7 @@ int main()
         OString aLanguages(getenv("ALL_LANGS"));
         if( aLanguages.isEmpty() )
         {
-            std::cerr << "Usage: bin/run pocheck\n";
+            std::cerr << "Usage: LD_LIBRARY_PATH=instdir/program make cmd cmd=workdir/LinkTarget/Executable/pocheck\n";
             return 1;
         }
         for(sal_Int32 i = 1;;++i) // skip en-US