android: Add host_cross_supported prop

Some modules are only intended to be build for the build host,
e.g. rust_library modules only used in rust_proc_macro or
code generators.

These should not be expected to be built for or supported on non-build
host platforms. Thus, add a host_cross_supported property to disable
the HostCross target.

Test: m blueprint_tests
Test: Modules with host_cross_supported: false don't build for HostCross
Change-Id: Ia15f55776e04d86aee19bb0dd0d27e1b985b2b75
diff --git a/android/arch_test.go b/android/arch_test.go
index f0a58a9..6134a06 100644
--- a/android/arch_test.go
+++ b/android/arch_test.go
@@ -332,6 +332,12 @@
 		}
 
 		module {
+			name: "nohostcross",
+			host_supported: true,
+			host_cross_supported: false,
+		}
+
+		module {
 			name: "baz",
 			device_supported: false,
 		}
@@ -355,13 +361,14 @@
 	`
 
 	testCases := []struct {
-		name          string
-		preparer      FixturePreparer
-		fooVariants   []string
-		barVariants   []string
-		bazVariants   []string
-		quxVariants   []string
-		firstVariants []string
+		name                string
+		preparer            FixturePreparer
+		fooVariants         []string
+		barVariants         []string
+		noHostCrossVariants []string
+		bazVariants         []string
+		quxVariants         []string
+		firstVariants       []string
 
 		multiTargetVariants    []string
 		multiTargetVariantsMap map[string][]string
@@ -373,6 +380,7 @@
 			preparer:            nil,
 			fooVariants:         []string{"android_arm64_armv8-a", "android_arm_armv7-a-neon"},
 			barVariants:         append(buildOSVariants, "android_arm64_armv8-a", "android_arm_armv7-a-neon"),
+			noHostCrossVariants: append(buildOSVariants, "android_arm64_armv8-a", "android_arm_armv7-a-neon"),
 			bazVariants:         nil,
 			quxVariants:         append(buildOS32Variants, "android_arm_armv7-a-neon"),
 			firstVariants:       append(buildOS64Variants, "android_arm64_armv8-a"),
@@ -390,6 +398,7 @@
 			}),
 			fooVariants:         nil,
 			barVariants:         buildOSVariants,
+			noHostCrossVariants: buildOSVariants,
 			bazVariants:         nil,
 			quxVariants:         buildOS32Variants,
 			firstVariants:       buildOS64Variants,
@@ -406,6 +415,7 @@
 			}),
 			fooVariants:         []string{"android_arm64_armv8-a", "android_arm_armv7-a-neon"},
 			barVariants:         []string{"linux_musl_x86_64", "linux_musl_arm64", "linux_musl_x86", "android_arm64_armv8-a", "android_arm_armv7-a-neon"},
+			noHostCrossVariants: []string{"linux_musl_x86_64", "linux_musl_x86", "android_arm64_armv8-a", "android_arm_armv7-a-neon"},
 			bazVariants:         nil,
 			quxVariants:         []string{"linux_musl_x86", "android_arm_armv7-a-neon"},
 			firstVariants:       []string{"linux_musl_x86_64", "linux_musl_arm64", "android_arm64_armv8-a"},
@@ -461,6 +471,10 @@
 				t.Errorf("want bar variants:\n%q\ngot:\n%q\n", w, g)
 			}
 
+			if g, w := enabledVariants(ctx, "nohostcross"), tt.noHostCrossVariants; !reflect.DeepEqual(w, g) {
+				t.Errorf("want nohostcross variants:\n%q\ngot:\n%q\n", w, g)
+			}
+
 			if g, w := enabledVariants(ctx, "baz"), tt.bazVariants; !reflect.DeepEqual(w, g) {
 				t.Errorf("want baz variants:\n%q\ngot:\n%q\n", w, g)
 			}