Include JDK library dex in incremental installs

When enable_jdk_library_desugaring=true and incremental_install=true,
a new dex file will appear in the APK containing classes related to JDK
library desugaring (as currently happens for non-incremental builds).

Note 1: Since Proguard shrinking doesn't apply to incremental installs,
the added dex file will be its full 400 kB size.

Note 2: The crash described in the bug doesn't occur if is_java_debug=true.

Bug: 1141199
Change-Id: Ib223abf168f7690ff1a5dfed5647521d10a2b42d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2492666
Commit-Queue: Ian Wells <iwells@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820045}

build/config/android/rules.gni

@@ -3189,7 +3189,8 @@ if (enable_java_templates) {
 
         deps = _deps + [ ":$_build_config_target" ]
 
-        if (!_proguard_enabled && enable_jdk_library_desugaring) {
+        if ((!_proguard_enabled || _incremental_apk) &&
+            enable_jdk_library_desugaring) {
           _all_jdk_libs = "//build/android:all_jdk_libs"
           deps += [ _all_jdk_libs ]
           jdk_libs_dex = get_label_info(_all_jdk_libs, "target_out_dir") +