Remove "exported" ninja variables

There was infrastructure to export ninja variables to bazel. Now that
the bazel migration is cancelled, we don't need it anymore.

Bug: 315353489
Test: m nothing
Change-Id: I298cc2ac7ebd004557be3b30d75f7357cab0b7a0
diff --git a/java/config/droidstubs.go b/java/config/droidstubs.go
index 39eec44..04a3f96 100644
--- a/java/config/droidstubs.go
+++ b/java/config/droidstubs.go
@@ -58,11 +58,7 @@
 )
 
 func init() {
-	exportedVars.ExportStringList("MetalavaFlags", metalavaFlags)
+	pctx.StaticVariable("MetalavaAnnotationsFlags", strings.Join(metalavaAnnotationsFlags, " "))
 
-	exportedVars.ExportString("MetalavaAddOpens", MetalavaAddOpens)
-
-	exportedVars.ExportStringListStaticVariable("MetalavaAnnotationsFlags", metalavaAnnotationsFlags)
-
-	exportedVars.ExportStringListStaticVariable("MetalavaAnnotationWarningsFlags", metalavaAnnotationsWarningsFlags)
+	pctx.StaticVariable("MetalavaAnnotationWarningsFlags", strings.Join(metalavaAnnotationsWarningsFlags, " "))
 }