tdf#117816, work around MS Excel bug with containsText cond format

Excel seems to require the formula that is equal to the containsText
condition.

According to cfRule (18.3.1.10) "Only rules with a type attribute
 value of expression support formula syntax." which contradicts the
MS EXCEL behavior.

Change-Id: Ifa3f9fee58194f70a64b37c62922513435d43bb8
Reviewed-on: https://gerrit.libreoffice.org/57432
Tested-by: Jenkins
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>

sc/source/filter/excel/xecontent.cxx

@@ -998,6 +998,16 @@ void XclExpCFImpl::SaveXml( XclExpXmlStream& rStrm )
             rWorksheet->endElement( XML_formula );
         }
     }
+    else if (IsTextRule(eOperation))
+    {
+        OStringBuffer aBufferOld;
+        OStringBuffer aBuffer = XclXmlUtils::ToOString(aBufferOld, mrFormatEntry.GetValidSrcPos());
+        OString aTextTopCell = aBuffer.makeStringAndClear();
+        OString aFormula = "NOT(ISERROR(SEARCH(\"" + aText + "\"," + aTextTopCell + ")))";
+        rWorksheet->startElement( XML_formula, FSEND );
+        rWorksheet->writeEscaped(aFormula.getStr());
+        rWorksheet->endElement( XML_formula );
+    }
     // OOXTODO: XML_extLst
     rWorksheet->endElement( XML_cfRule );
 }