Add back the llvm-ar P flag

The P flag is supported as of llvm r354044, add back the flag to reduce
the size of intermediate archieve files. This does not affect the final
binaries.

Test: built
Bug: 71618641
Change-Id: I017780e4dcaa31c7fbe10b5e7482db1bba83e716

cc/builder.go

@@ -551,7 +551,7 @@ func TransformObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
 	flags builderFlags, outputFile android.ModuleOutPath, deps android.Paths) {
 
 	arCmd := "${config.ClangBin}/llvm-ar"
-	arFlags := "crsD"
+	arFlags := "crsPD"
 	if !ctx.Darwin() {
 		arFlags += " -format=gnu"
 	}