trees: fix bad comparison in configure_project()

we used to set cmd only to these values:
build_project
build_targets

however, now we set them to:
build_project
build_targets $@

the latter cannot be measured reliably, but
we were checking whether cmd equalled:
build_targets

now we instead check that it does not equal:
build_project

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/trees

@@ -122,7 +122,7 @@ configure_project()
 	[ -f "$datadir/mkhelper.cfg" ] && eval `setcfg "$datadir/mkhelper.cfg"`
 
 	_tcfg="$1/target.cfg"
-	while [ -f "$_tcfg" ] || [ "$cmd" = "build_targets" ]; do
+	while [ -f "$_tcfg" ] || [ "$cmd" != "build_project" ]; do
 		eval `setvars "" rev tree`
 
 		printf "Loading %s config: %s\n" "$project" "$_tcfg"