Fix glib_subprocess test

A typo means that the tests dependent on glib with subprocess
support are never run.

Fixes: 9d41401b90fa10b335d2e739149d36437cfbf622

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

configure

diff --git a/configure b/configure
index 6fed07b..fe3440f 100755
--- a/configure
+++ b/configure
@@ -4822,7 +4822,7 @@
   echo "CONFIG_BLUEZ=y" >> $config_host_mak
   echo "BLUEZ_CFLAGS=$bluez_cflags" >> $config_host_mak
 fi
-if test "glib_subprocess" = "yes" ; then
+if test "$glib_subprocess" = "yes" ; then
   echo "CONFIG_HAS_GLIB_SUBPROCESS_TESTS=y" >> $config_host_mak
 fi
 echo "GLIB_CFLAGS=$glib_cflags" >> $config_host_mak