package/waf: bump to v2.0.21

Also add a comment in waf.hash about the mechanism for LICENSE hash check

Signed-off-by: Titouan Christophe <titouanchristophe@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/waf/waf.hash

@@ -1,4 +1,7 @@
 # Locally computed
-sha1  92212071a63ce38fdfd69fb8332f04e84d1f6635  waf-2.0.20
-sha256  bf971e98edc2414968a262c6aa6b88541a26c3cd248689c89f4c57370955ee7f  waf-2.0.20
-sha256  bf971e98edc2414968a262c6aa6b88541a26c3cd248689c89f4c57370955ee7f  waf
+sha1  b7f38d2987433ee6e0f4a75ecec8807575176e1e  waf-2.0.21
+sha256  7cebf2c5efe53cbb9a4b5bdc4b49ae90ecd64a8fce7a3222d58e591b58215306  waf-2.0.21
+
+# The waf script also contains its license, but is renamed `waf` in the extract
+# step, so this is a synonym for the above, to check WAF_LICENSE
+sha256  7cebf2c5efe53cbb9a4b5bdc4b49ae90ecd64a8fce7a3222d58e591b58215306  waf

package/waf/waf.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-WAF_VERSION = 2.0.20
+WAF_VERSION = 2.0.21
 WAF_SOURCE = waf-$(WAF_VERSION)
 WAF_SITE = https://waf.io
 WAF_LICENSE = BSD-3-Clause