build: support CentOS Stream 9

Change-Id: I8864a856b4f777110cea37528d963e9eb77ed973
diff --git a/wscript b/wscript
index 270ac19..4253101 100644
--- a/wscript
+++ b/wscript
@@ -39,7 +39,12 @@
     conf.env.WITH_EXAMPLES = conf.options.with_examples
     conf.env.WITH_TESTS = conf.options.with_tests
 
-    conf.find_program('dot', var='DOT', mandatory=False)
+    conf.find_program('dot', mandatory=False)
+
+    # Prefer pkgconf if it's installed, because it gives more correct results
+    # on Fedora/CentOS/RHEL/etc. See https://bugzilla.redhat.com/show_bug.cgi?id=1953348
+    # Store the result in env.PKGCONFIG, which is the variable used inside check_cfg()
+    conf.find_program(['pkgconf', 'pkg-config'], var='PKGCONFIG')
 
     pkg_config_path = os.environ.get('PKG_CONFIG_PATH', f'{conf.env.LIBDIR}/pkgconfig')
     conf.check_cfg(package='libndn-cxx', args=['libndn-cxx >= 0.8.0', '--cflags', '--libs'],