Windows: Android BusyBox can access the JNI lib

Add a data-dependency on the windows_jni.dll from
the BusyBox in BUILD.tools, so the BusyBox in
@build_tools// can actually find it at runtime.

Also update the script that builds the .dll so
that it works if the source files have an
"external/bazel_tools/" prefix.

Related to https://github.com/bazelbuild/bazel/issues/3264

Change-Id: I005e9d2c00253a59d2cd5cc9f3a93528dc4d2e9e
PiperOrigin-RevId: 163691320

2 files changed, 24 insertions, 5 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/windows/jni/WindowsJniLoader.java b/src/main/java/com/google/devtools/build/lib/windows/jni/WindowsJniLoader.java
index 974fe4e6dc..d53a10c479 100644
--- a/src/main/java/com/google/devtools/build/lib/windows/jni/WindowsJniLoader.java
+++ b/src/main/java/com/google/devtools/build/lib/windows/jni/WindowsJniLoader.java
@@ -30,13 +30,31 @@ public class WindowsJniLoader {
       System.loadLibrary("windows_jni");
     } catch (UnsatisfiedLinkError ex) {
       // Try to find the library in the runfiles.
-      try {
-        System.load(WindowsRunfiles.getRunfile("io_bazel/src/main/native/windows/windows_jni.dll"));
-      } catch (IOException e) {
-        // We throw the UnsatisfiedLinkError if we cannot find the runfiles
-        throw ex;
+      if (!loadFromRunfileOrThrow("io_bazel/src/main/native/windows/windows_jni.dll", ex)) {
+        if (!loadFromRunfileOrThrow(
+            "io_bazel/external/bazel_tools/src/main/native/windows/windows_jni.dll", ex)) {
+          // We throw the UnsatisfiedLinkError if we cannot find the DLL under any known location.
+          throw ex;
+        }
       }
     }
     jniLoaded = true;
   }
+
+  private static boolean loadFromRunfileOrThrow(String runfile, UnsatisfiedLinkError ex) {
+    // Try to find the library in the runfiles.
+    String path;
+    try {
+      path = WindowsRunfiles.getRunfile(runfile);
+      if (path == null) {
+        // Just return false if the runfile path was not found. Maybe it's under a different path.
+        return false;
+      }
+      System.load(path);
+      return true;
+    } catch (IOException e) {
+      // We throw the UnsatisfiedLinkError if we cannot find the runfiles
+      throw ex;
+    }
+  }
 }
diff --git a/src/tools/android/java/com/google/devtools/build/android/BUILD.tools b/src/tools/android/java/com/google/devtools/build/android/BUILD.tools
index a8670b12b4..e67a400f97 100644
--- a/src/tools/android/java/com/google/devtools/build/android/BUILD.tools
+++ b/src/tools/android/java/com/google/devtools/build/android/BUILD.tools
@@ -11,4 +11,5 @@ java_binary(
     runtime_deps = [
         ":classes",
     ],
+    data = ["//src/main/native/windows:windows_jni.dll"],
 )