create top-level .qmake.super instead of .qmake.cache

at this point, the cache is needed only to aggregate the modules,
not to "export" qtbase internals. the modules now have private caches
for "real" config data.

Change-Id: I4c70d220bbc054023710680545a04c171e238aff
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@nokia.com>

configure

@@ -108,9 +108,5 @@ if (! -e ".qmake.cache") {
 
 chdir("$outpath");
 
-open QMAKE_CACHE, ">.qmake.cache" || die "Could not open .qmake.cache for writing!\n";
-print QMAKE_CACHE "include(\$\$PWD/qtbase/.qmake.cache)\n";
-close QMAKE_CACHE;
-
 $ret = system_v("$outpath/qtbase/bin/qmake $relpath/qt.pro");
 exit ($ret>>8);

qt.pro

+# Create the super cache so modules will add themselves to it.
+cache(, super)
+
 TEMPLATE      = subdirs
 
 module_qtbase.subdir = qtbase