Put grepped_includes file into a separate directory for tree file art…

…ifacts also in async mode.

This was missed in e6f2f5b

RELNOTES: None.
PiperOrigin-RevId: 267587005

src/main/java/com/google/devtools/build/lib/includescanning/SpawnIncludeScanner.java

@@ -393,8 +393,9 @@ public ListenableFuture<Collection<Inclusion>> extractInclusionsAsync(
       ActionExecutionContext actionExecutionContext,
       Artifact grepIncludes,
       GrepIncludesFileType fileType,
-      boolean placeNextToFile)
+      boolean isOutputFile)
       throws IOException {
+    boolean placeNextToFile = isOutputFile && !file.hasParent();
     Path output =
         getIncludesOutput(
             file, actionExecutionContext.getPathResolver(), fileType, placeNextToFile);