support/scripts/pkg-stats: Don't print directory in 'make' call

It is possible that some users of buildroot have put it in a repository
and call into it from another Makefile such as:
.DEFAULT:
	$(MAKE) O=$(abspath $(O)) -C buildroot $(@)

This technique works well except that Make tells us that it changes into
the buildroot directory:
make[1]: Entering directory 'buildroot'

Because this line doesn't have an equals within it, python raises a
ValueError exception within pkg-stats.

This patch has python tell the invoked make not to print directories

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

support/scripts/pkg-stats

@@ -375,7 +375,8 @@ def get_config_packages():
 
 def package_init_make_info():
     # Fetch all variables at once
-    variables = subprocess.check_output(["make", "BR2_HAVE_DOT_CONFIG=y", "-s", "printvars",
+    variables = subprocess.check_output(["make", "--no-print-directory", "-s",
+                                         "BR2_HAVE_DOT_CONFIG=y", "printvars",
                                          "VARS=%_LICENSE %_LICENSE_FILES %_VERSION %_IGNORE_CVES %_CPE_ID"])
     variable_list = variables.decode().splitlines()