Stop using single-hyphen metalava options

`-encoding` and `-source` have been deprecated in metalava.

`-encoding` actually does nothing apart from check to make sure that
the value is `utf-8` (in some case). Metalava always uses `utf-8`.

`-source` has been deprecated in favor of `--java-source` as metalava
also can consume kotlin and it has its own `--kotlin-source` option.

Bug: 295136054
Test: ./gradlew
Change-Id: I08e6931958f40022d65d417360e32b72a1d70444

java/droiddoc.go

@@ -699,7 +699,6 @@ func javadocCmd(ctx android.ModuleContext, rule *android.RuleBuilder, srcs andro
 	cmd := rule.Command().
 		BuiltTool("soong_javac_wrapper").Tool(config.JavadocCmd(ctx)).
 		Flag(config.JavacVmFlags).
-		FlagWithArg("-encoding ", "UTF-8").
 		FlagWithRspFileInputList("@", android.PathForModuleOut(ctx, "javadoc.rsp"), srcs).
 		FlagWithInput("@", srcJarList)
 

java/droidstubs.go

@@ -512,8 +512,7 @@ func metalavaCmd(ctx android.ModuleContext, rule *android.RuleBuilder, javaVersi
 	cmd.BuiltTool("metalava").ImplicitTool(ctx.Config().HostJavaToolPath(ctx, "metalava.jar")).
 		Flag(config.JavacVmFlags).
 		Flag("-J--add-opens=java.base/java.util=ALL-UNNAMED").
-		FlagWithArg("-encoding ", "UTF-8").
-		FlagWithArg("-source ", javaVersion.String()).
+		FlagWithArg("--java-source ", javaVersion.String()).
 		FlagWithRspFileInputList("@", android.PathForModuleOut(ctx, "metalava.rsp"), srcs).
 		FlagWithInput("@", srcJarList)
 

java/java.go

@@ -1725,7 +1725,6 @@ func metalavaStubCmd(ctx android.ModuleContext, rule *android.RuleBuilder,
 	cmd.BuiltTool("metalava").ImplicitTool(ctx.Config().HostJavaToolPath(ctx, "metalava.jar")).
 		Flag(config.JavacVmFlags).
 		Flag("-J--add-opens=java.base/java.util=ALL-UNNAMED").
-		FlagWithArg("-encoding ", "UTF-8").
 		FlagWithInputList("--source-files ", srcs, " ")
 
 	cmd.Flag("--color").