apparmor: explain makefile fix

srcpkgs/apparmor/template

@@ -24,6 +24,12 @@ if [ -z "$CROSS_BUILD" ]; then
 fi
 
 post_patch() {
+	# Make.rules feeds some system headers to the C preprocessor to produce
+	# lists of capability and address-family names that, respectively,
+	# populate `parser/cap_names.h` and `parser/af_names.h`. The escaping
+	# backslash in the '\#include" directives here is seen by the
+	# preprocessor, causing it to skip the system headers and produce empty
+	# files. Removing the backslash ensures correct behavior.
 	vsed -i ${wrksrc}/common/Make.rules -e 's/\\#include </#include </'
 }