[aapt2] Set use_version_lib.

This is needed by the build system to update soong_build_number.

On a local build, "aapt2 version" used to print:
  Android Asset Packaging Tool (aapt) 2.19-SOONG BUILD NUMBER PLACEHOLDER
Now it prints:
  Android Asset Packaging Tool (aapt) 2.19-eng.dchai.20190511.023434

Bug: 132476779
Bug: 123663089
Change-Id: I5bc5adc9f5b2a7a30bdc649e3c073868b55f17df
Tested: manual, see above
diff --git a/tools/aapt2/Android.bp b/tools/aapt2/Android.bp
index 53372bf..b13731f 100644
--- a/tools/aapt2/Android.bp
+++ b/tools/aapt2/Android.bp
@@ -197,6 +197,7 @@
 cc_binary_host {
     name: "aapt2",
     srcs: ["Main.cpp"] + toolSources,
+    use_version_lib: true,
     static_libs: ["libaapt2"],
     defaults: ["aapt2_defaults"],
 }