Remove obsolete PDK build functionality

This hasn't worked for a couple years, and continues to bitrot. Just
remove it.

Adds a bpfix rule so that we can eventually remove the
product_variables.pdk definition, which is now always a no-op.

Test: treehugger
Change-Id: I830b54d419b59f6db1d4617b45e61a78234f57a7
Merged-In: I830b54d419b59f6db1d4617b45e61a78234f57a7
diff --git a/ui/build/kati.go b/ui/build/kati.go
index 1cd5fea..f6d3a57 100644
--- a/ui/build/kati.go
+++ b/ui/build/kati.go
@@ -134,14 +134,10 @@
 
 	args := []string{
 		"--writable", config.OutDir() + "/",
+		"--werror_implicit_rules",
 		"-f", "build/make/core/main.mk",
 	}
 
-	// PDK builds still uses a few implicit rules
-	if !config.IsPdkBuild() {
-		args = append(args, "--werror_implicit_rules")
-	}
-
 	if !config.BuildBrokenDupRules() {
 		args = append(args, "--werror_overriding_commands")
 	}