Disable the JSC portion of the test unless we have a system PCRE

CONFIG += pcre is enabled if we're using the Qt PCRE, which isn't
compiled for 8-bit. If it isn't set, then we have a system PCRE.

Change-Id: I29d043b9d3f4d3223dcbb41eadc9f859e710eb88
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

tests/benchmarks/corelib/tools/qregexp/qregexp.pro

@@ -6,7 +6,7 @@ CONFIG += release exceptions
 SOURCES += main.cpp
 RESOURCES += qregexp.qrc
 
-!isEmpty(QT.script.name) {
+!isEmpty(QT.script.name):!pcre {
     DEFINES += HAVE_JSC
     QT += script
 }