Distinguish boot images by target rather than arch

We plan to add boot image variants for host tests.
Distinguishing the variants by arch does not work,
since both host and device can have the same arch.

(cherry picked from commit c177ebeca9811057ac3c757e1c3e07724b8ece4d)

Test: m
Bug: 152037801
Merged-In: Iea73c77367affb074f97a0fc318389417ce537da
Change-Id: I8b95882bb00cd2fd1f6cfd8a2784f9ebb957eec6
diff --git a/java/dexpreopt_config.go b/java/dexpreopt_config.go
index 5d74b21..f8356d1 100644
--- a/java/dexpreopt_config.go
+++ b/java/dexpreopt_config.go
@@ -139,8 +139,6 @@
 
 		// common to all configs
 		for _, c := range configs {
-			c.targets = targets
-
 			c.dir = deviceDir.Join(ctx, "dex_"+c.name+"jars")
 			c.symbolsDir = deviceDir.Join(ctx, "dex_"+c.name+"jars_unstripped")
 
@@ -159,14 +157,17 @@
 			}
 			c.dexPathsDeps = c.dexPaths
 
-			c.images = make(map[android.ArchType]android.OutputPath)
-			c.imagesDeps = make(map[android.ArchType]android.OutputPaths)
-
+			// Create target-specific variants.
 			for _, target := range targets {
 				arch := target.Arch.ArchType
 				imageDir := c.dir.Join(ctx, c.installSubdir, arch.String())
-				c.images[arch] = imageDir.Join(ctx, imageName)
-				c.imagesDeps[arch] = c.moduleFiles(ctx, imageDir, ".art", ".oat", ".vdex")
+				variant := &bootImageVariant{
+					bootImageConfig: c,
+					target:          target,
+					images:          imageDir.Join(ctx, imageName),
+					imagesDeps:      c.moduleFiles(ctx, imageDir, ".art", ".oat", ".vdex"),
+				}
+				c.variants = append(c.variants, variant)
 			}
 
 			c.zip = c.dir.Join(ctx, c.name+".zip")
@@ -174,19 +175,21 @@
 
 		// specific to the framework config
 		frameworkCfg.dexPathsDeps = append(artCfg.dexPathsDeps, frameworkCfg.dexPathsDeps...)
-		frameworkCfg.primaryImages = artCfg.images
+		for i := range targets {
+			frameworkCfg.variants[i].primaryImages = artCfg.variants[i].images
+		}
 		frameworkCfg.imageLocations = append(artCfg.imageLocations, frameworkCfg.imageLocations...)
 
 		return configs
 	}).(map[string]*bootImageConfig)
 }
 
-func artBootImageConfig(ctx android.PathContext) bootImageConfig {
-	return *genBootImageConfigs(ctx)[artBootImageName]
+func artBootImageConfig(ctx android.PathContext) *bootImageConfig {
+	return genBootImageConfigs(ctx)[artBootImageName]
 }
 
-func defaultBootImageConfig(ctx android.PathContext) bootImageConfig {
-	return *genBootImageConfigs(ctx)[frameworkBootImageName]
+func defaultBootImageConfig(ctx android.PathContext) *bootImageConfig {
+	return genBootImageConfigs(ctx)[frameworkBootImageName]
 }
 
 func defaultBootclasspath(ctx android.PathContext) []string {