tests: add missing dependency to build QTEST_QEMU_BINARY, round 2

In commit b94b330e ("tests: add missing dependency to build
QTEST_QEMU_BINARY", 2017-07-31), Phil fixed the dependency list of make
target "check-qtest-%". Namely, the recipe would set QTEST_QEMU_BINARY to
the softmmu emulator for the emulation target, but the prerequisites
didn't include the emulator.

The same issue affects the "check-report-qtest-%.tap" make target, which
is the other make target whose recipe sets QTEST_QEMU_BINARY:

> $ make -j4 check-report-qtest-aarch64.tap
>   TAP     check-report-qtest-aarch64.tap
> sh: /.../aarch64-softmmu/qemu-system-aarch64: No such file or directory

Apply Phil's fix to this make target too.
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>
Tested-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daud <philmd@redhat.com>
Tested-by: NPhilippe Mathieu-Daud <philmd@redhat.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>

tests/Makefile.include

@@ -912,7 +912,7 @@ check-speed: $(check-speed-y)
 
 # gtester tests with TAP output
 
-$(patsubst %, check-report-qtest-%.tap, $(QTEST_TARGETS)): check-report-qtest-%.tap: $(check-qtest-y)
+$(patsubst %, check-report-qtest-%.tap, $(QTEST_TARGETS)): check-report-qtest-%.tap: subdir-%-softmmu $(check-qtest-y)
 	$(call do_test_tap, $(check-qtest-$*-y) $(check-qtest-generic-y), \
 	  QTEST_QEMU_BINARY=$*-softmmu/qemu-system-$* \
 	  QTEST_QEMU_IMG=qemu-img$(EXESUF))