[7.3.0] Ignore transitive cppmap files from dotd files (bazelbuild#23122

)

When clang generates dotd files when using `-fmodule-map-file` any
`extern module` directives in the modulemap are included in the dotd
file if they exist. The result of this was that with sandboxing disabled
the dotd file included transitive cppmap files that weren't in its input
set, resulting in build failures. This change excludes those instead
since they're not required as evidence by the fact that with sandboxing
enabled they are not part of the input set.

Fixes bazelbuild#21592

Closes bazelbuild#21832.

PiperOrigin-RevId: 656382428
Change-Id: I4bc9802884ce1bc66ceda65a602db8dffbd1d9ea

Commit
bazelbuild@ad53147

Co-authored-by: Keith Smiley <[email protected]>

src/main/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscovery.java

@@ -189,6 +189,12 @@ private static NestedSet<Artifact> runDiscovery(
           inputs.add(artifact);
         }
         continue;
+      } else if (artifact == null && execPathFragment.getFileExtension().equals("cppmap")) {
+        // Transitive cppmap files are added to the dotd files of compiles even
+        // though they are not required for compilation. Since they're not
+        // explicit inputs to the action this only happens when sandboxing is
+        // disabled.
+        continue;
       }
 
       SpecialArtifact treeArtifact = findOwningTreeArtifact(execPathFragment, treeArtifacts);

src/test/shell/bazel/bazel_layering_check_test.sh

@@ -166,6 +166,11 @@ function test_bazel_layering_check() {
     fail "module map files were not generated"
   fi
 
+  CC="${clang_tool}" bazel build \
+    //hello:hello --copt=-DFORCE_REBUILD=1 \
+    --spawn_strategy=local --features=layering_check \
+    &> "${TEST_log}" || fail "Build with layering_check failed without sandboxing"
+
   CC="${clang_tool}" bazel build \
     --copt=-D=private_header \
     //hello:hello --features=layering_check \