Export dex implementation jars from prebuilt_apex

Dexpreopt and boot jars package check all require access to dex
implementation jars created for java_library and java_sdk_library. They
were available when building from source but not when building from
prebuilts, even though they are embedded within the .apex files that
are referenced from prebuilt_apex.

This changes adds support to prebuilt_apex to export the dex
implementation jars and updates java_import to use those exported dex
implementation jars.

In a source build dexpreopt/boot jars package check access the apex (or
platform) specific variant of a java_library, e.g. core-oj, from which
it retrieves the dex implementation jar path.

After this change in a prebuilt build dexpreopt/boot jars package check
behave in the same way except in this case they retrieve the dex
implementation jar path from the apex (or platform) specific variant of
the java_import, e.g. core-oj.

The work to export files from a `.apex` file for use by other modules
is performed by a new `deapexer` module type. It is not used directly
in an `Android.bp` file but instead is created implicitly by
`prebuilt_apex`,

In order to do that this contains the following changes:
* Adds a new `dexapexer` module type to handle the exporting of files
  from the `.apex` file.
* Adds an exported_java_libs property to prebuilt_apex to specify the
  set of libraries whose dex implementation jars need exporting.
* Creates apex specific variants of the libraries listed in the
  exported_java_libs property.
* Adds the set of exported files to the ApexInfo to make them available
  to the apex specific variants.
* Prevents the prebuilt_apex variants from being merged together as
  they will not be compatible.
* Modifies java_import to use the exported file for variants of a
  prebuilt_apex.
* Adds a ninja rule to unpack (using deapexer) the contents of the
  prebuilt_apex's apex file, verify that the required files are present
  and make them available as outputs for other rules to use.
* Some minor refactorings to support these changes.
* Adds tests to cover prebuilt only, prebuilt with source preferred,
  and prebuilt preferred with source.

Test: m nothing
Bug: 171061220
Change-Id: Ic9bed81fb65b92f0d59f64c0bce168a9ed44cfac

android/apex_test.go

@@ -20,6 +20,10 @@ import (
 )
 
 func Test_mergeApexVariations(t *testing.T) {
+	const (
+		ForPrebuiltApex    = true
+		NotForPrebuiltApex = false
+	)
 	tests := []struct {
 		name        string
 		in          []ApexInfo
@@ -29,10 +33,10 @@ func Test_mergeApexVariations(t *testing.T) {
 		{
 			name: "single",
 			in: []ApexInfo{
-				{"foo", "current", false, nil, []string{"foo"}, nil},
+				{"foo", "current", false, nil, []string{"foo"}, nil, NotForPrebuiltApex},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000", "current", false, nil, []string{"foo"}, nil},
+				{"apex10000", "current", false, nil, []string{"foo"}, nil, NotForPrebuiltApex},
 			},
 			wantAliases: [][2]string{
 				{"foo", "apex10000"},
@@ -41,11 +45,11 @@ func Test_mergeApexVariations(t *testing.T) {
 		{
 			name: "merge",
 			in: []ApexInfo{
-				{"foo", "current", false, SdkRefs{{"baz", "1"}}, []string{"foo"}, nil},
-				{"bar", "current", false, SdkRefs{{"baz", "1"}}, []string{"bar"}, nil},
+				{"foo", "current", false, SdkRefs{{"baz", "1"}}, []string{"foo"}, nil, NotForPrebuiltApex},
+				{"bar", "current", false, SdkRefs{{"baz", "1"}}, []string{"bar"}, nil, NotForPrebuiltApex},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000_baz_1", "current", false, SdkRefs{{"baz", "1"}}, []string{"bar", "foo"}, nil}},
+				{"apex10000_baz_1", "current", false, SdkRefs{{"baz", "1"}}, []string{"bar", "foo"}, nil, false}},
 			wantAliases: [][2]string{
 				{"bar", "apex10000_baz_1"},
 				{"foo", "apex10000_baz_1"},
@@ -54,12 +58,12 @@ func Test_mergeApexVariations(t *testing.T) {
 		{
 			name: "don't merge version",
 			in: []ApexInfo{
-				{"foo", "current", false, nil, []string{"foo"}, nil},
-				{"bar", "30", false, nil, []string{"bar"}, nil},
+				{"foo", "current", false, nil, []string{"foo"}, nil, NotForPrebuiltApex},
+				{"bar", "30", false, nil, []string{"bar"}, nil, NotForPrebuiltApex},
 			},
 			wantMerged: []ApexInfo{
-				{"apex30", "30", false, nil, []string{"bar"}, nil},
-				{"apex10000", "current", false, nil, []string{"foo"}, nil},
+				{"apex30", "30", false, nil, []string{"bar"}, nil, NotForPrebuiltApex},
+				{"apex10000", "current", false, nil, []string{"foo"}, nil, NotForPrebuiltApex},
 			},
 			wantAliases: [][2]string{
 				{"bar", "apex30"},
@@ -69,11 +73,11 @@ func Test_mergeApexVariations(t *testing.T) {
 		{
 			name: "merge updatable",
 			in: []ApexInfo{
-				{"foo", "current", false, nil, []string{"foo"}, nil},
-				{"bar", "current", true, nil, []string{"bar"}, nil},
+				{"foo", "current", false, nil, []string{"foo"}, nil, NotForPrebuiltApex},
+				{"bar", "current", true, nil, []string{"bar"}, nil, NotForPrebuiltApex},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000", "current", true, nil, []string{"bar", "foo"}, nil},
+				{"apex10000", "current", true, nil, []string{"bar", "foo"}, nil, NotForPrebuiltApex},
 			},
 			wantAliases: [][2]string{
 				{"bar", "apex10000"},
@@ -83,19 +87,38 @@ func Test_mergeApexVariations(t *testing.T) {
 		{
 			name: "don't merge sdks",
 			in: []ApexInfo{
-				{"foo", "current", false, SdkRefs{{"baz", "1"}}, []string{"foo"}, nil},
-				{"bar", "current", false, SdkRefs{{"baz", "2"}}, []string{"bar"}, nil},
+				{"foo", "current", false, SdkRefs{{"baz", "1"}}, []string{"foo"}, nil, NotForPrebuiltApex},
+				{"bar", "current", false, SdkRefs{{"baz", "2"}}, []string{"bar"}, nil, NotForPrebuiltApex},
 			},
 			wantMerged: []ApexInfo{
-				{"apex10000_baz_2", "current", false, SdkRefs{{"baz", "2"}}, []string{"bar"}, nil},
-				{"apex10000_baz_1", "current", false, SdkRefs{{"baz", "1"}}, []string{"foo"}, nil},
+				{"apex10000_baz_2", "current", false, SdkRefs{{"baz", "2"}}, []string{"bar"}, nil, NotForPrebuiltApex},
+				{"apex10000_baz_1", "current", false, SdkRefs{{"baz", "1"}}, []string{"foo"}, nil, NotForPrebuiltApex},
 			},
 			wantAliases: [][2]string{
 				{"bar", "apex10000_baz_2"},
 				{"foo", "apex10000_baz_1"},
 			},
 		},
+		{
+			name: "don't merge when for prebuilt_apex",
+			in: []ApexInfo{
+				{"foo", "current", false, nil, []string{"foo"}, nil, NotForPrebuiltApex},
+				{"bar", "current", true, nil, []string{"bar"}, nil, NotForPrebuiltApex},
+				// This one should not be merged in with the others because it is for
+				// a prebuilt_apex.
+				{"baz", "current", true, nil, []string{"baz"}, nil, ForPrebuiltApex},
+			},
+			wantMerged: []ApexInfo{
+				{"apex10000", "current", true, nil, []string{"bar", "foo"}, nil, NotForPrebuiltApex},
+				{"baz", "current", true, nil, []string{"baz"}, nil, ForPrebuiltApex},
+			},
+			wantAliases: [][2]string{
+				{"bar", "apex10000"},
+				{"foo", "apex10000"},
+			},
+		},
 	}
+
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			config := TestConfig(buildDir, nil, "", nil)