Merge "Use combined.ninja for soong_docs null build test." am: 5470d24ab7

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/1802328

Change-Id: I6e98c499e18ddabc9b083b1aa36fc4a75f2657c8
diff --git a/tests/bootstrap_test.sh b/tests/bootstrap_test.sh
index 9342d75..76b2ee9 100755
--- a/tests/bootstrap_test.sh
+++ b/tests/bootstrap_test.sh
@@ -477,7 +477,8 @@
   run_soong
   local mtime1=$(stat -c "%y" out/soong/build.ninja)
 
-  prebuilts/build-tools/linux-x86/bin/ninja -f out/soong/build.ninja soong_docs
+  prebuilts/build-tools/linux-x86/bin/ninja -f out/combined.ninja soong_docs
+
   run_soong
   local mtime2=$(stat -c "%y" out/soong/build.ninja)