configure: Prepend pixman and ftd flags to overrule system-provided ones

Other packages may provide includes for pixman as well if the host has a
devel package installed. So add ours to the front to unsure that the
right version is used.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

configure

@@ -4211,9 +4211,9 @@ EOF
   fi
 fi
 
-# add pixman flags after all config tests are done
-QEMU_CFLAGS="$QEMU_CFLAGS $pixman_cflags $fdt_cflags"
-libs_softmmu="$libs_softmmu $pixman_libs"
+# prepend pixman and ftd flags after all config tests are done
+QEMU_CFLAGS="$pixman_cflags $fdt_cflags $QEMU_CFLAGS"
+libs_softmmu="$pixman_libs $libs_softmmu"
 
 echo "Install prefix    $prefix"
 echo "BIOS directory    `eval echo $qemu_datadir`"