Fixed tst_qobject signalbug silently not compiled in -fast builds.

Fixed tst_qobject signalbug silently not compiled in -fast builds.

When configuring with -fast on Windows, a directory which contains two
.pro files, one SUBDIRS and one not, will have the SUBDIRS Makefile
silently clobbered by the non-SUBDIRS Makefile.  In practice, this may
cause various subdirectories to be silently excluded from the build.

Rearrange .pro files for this test to avoid triggering this bug.

See also  e9015b3bc8827a8276f58bdd41adcac1bcbf2137.

Task-number: QTBUG-21168

Change-Id: I18fac1ac636fdc6b2aaee1b4cdfee9c4bc2a77ff
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>