Convert api.xml dist rules to Soong

...from make to support dist'ing *-api.xml files in soong-only builds.

Test: m droid dist --soong-only && ls out/dist/api.xml
Bug: 395162087
Bug: 394365683
Change-Id: I98e92423a107d24b04e6f6f0f96c23c24de01fa5
diff --git a/java/builder.go b/java/builder.go
index 22dad10..ade9784 100644
--- a/java/builder.go
+++ b/java/builder.go
@@ -323,6 +323,13 @@
 			Command:     `${keep-flagged-apis} ${in} > ${out}`,
 			CommandDeps: []string{"${keep-flagged-apis}"},
 		})
+
+	generateApiXMLRule = pctx.AndroidStaticRule("generateApiXMLRule",
+		blueprint.RuleParams{
+			Command:     `${config.JavaCmd} ${config.JavaVmFlags} -Xmx4g -jar ${config.MetalavaJar} jar-to-jdiff ${in} ${out}`,
+			CommandDeps: []string{"${config.JavaCmd}", "${config.MetalavaJar}"},
+			Description: "Converting API file to XML",
+		})
 )
 
 func init() {