Ensure that genrule's host tool deps are for host

Previously, when gathering transitive dependencies of genrule's host
tool, TransitivePackagingSpecs() was used if available. However, when
using this, it didn't check whether the dependencies are for host or not
(i.e. device). This was fine because host module can only depend on host
modules.

However, this is preventing Soong from implementing the installation of
the required modules by itself. Then a host module may depend on a
device module or vice versa (because that's the symantics of the
property).

To prevent the issue, check the partition of the transitive dependencies
of the host tool and filter out ones whose partition is not "" (which
means host).

Bug: 321626681
Test: builds
Change-Id: I296a920b3b88e7601315a4e1768af9727d0061e6

genrule/genrule.go

@@ -317,7 +317,17 @@ func (g *Module) generateCommonBuildActions(ctx android.ModuleContext) {
 						// required relative locations of the tool and its dependencies, use those
 						// instead.  They will be copied to those relative locations in the sbox
 						// sandbox.
-						packagedTools = append(packagedTools, specs...)
+						// Care must be taken since TransitivePackagingSpec may return device-side
+						// paths via the required property. Filter them out.
+						for i, ps := range specs {
+							if ps.Partition() != "" {
+								if i == 0 {
+									panic("first PackagingSpec is assumed to be the host-side tool")
+								}
+								continue
+							}
+							packagedTools = append(packagedTools, ps)
+						}
 						// Assume that the first PackagingSpec of the module is the tool.
 						addLocationLabel(tag.label, packagedToolLocation{specs[0]})
 					} else {