abuild: add warning when pc:* provider is missing

and indicate which package that should provide it and needs a rebuild.

abuild.in

@@ -1047,13 +1047,16 @@ trace_apk_deps() {
 
 	# pkg-config depends
 	for i in $(sort -u "$dir"/.needs-pc 2>/dev/null); do
-		if grep -w "^depend = ${i%[<>=]*}$" "$dir"/.PKGINFO >/dev/null ; then
-			warning "You can remove '$i' from depends"
-			continue
-		fi
 		if subpkg_provides_pc "$i" || cross_compiling \
 				|| $APK info --quiet --installed "pc:$i"; then
 			autodeps="$autodeps pc:$i"
+		else
+			warning "Could not find any provider for pc:$i"
+			local pcfile=/usr/lib/pkgconfig/"${i%%[<>=]*}".pc
+			if [ -e "$pcfile" ]; then
+				local owner=$($APK info --quiet --who-owns $pcfile)
+				warning "${owner:-package providing $pcfile} needs to be rebuilt"
+			fi
 		fi
 	done