Skip dexbootjar check using AllowMissingDependencies flag

Soong checks that every module part of a bootclass_fragment provides a
dex boot jar file, even if the module is not a dependency of vendor.img

Using AllowMissingDepdencies() to skip this check allows vendors to be
more aggressive in removing projects from their source tree

Test: In build/soong, run go test ./...
Test: m nothing
Bug: 196306898
Bug: 192616764
Change-Id: I78b062afdc19a6a3251aa8552230f3fcf334b6fb

apex/apex_test.go

@@ -5090,6 +5090,12 @@ func TestBootDexJarsFromSourcesAndPrebuilts(t *testing.T) {
 		// find the dex boot jar in it. We either need to disable the source libfoo
 		// or make the prebuilt libfoo preferred.
 		testDexpreoptWithApexes(t, bp, "module libfoo does not provide a dex boot jar", preparer, fragment)
+		// dexbootjar check is skipped if AllowMissingDependencies is true
+		preparerAllowMissingDeps := android.GroupFixturePreparers(
+			preparer,
+			android.PrepareForTestWithAllowMissingDependencies,
+		)
+		testDexpreoptWithApexes(t, bp, "", preparerAllowMissingDeps, fragment)
 	})
 
 	t.Run("prebuilt library preferred with source", func(t *testing.T) {

java/dexpreopt_bootjars.go

@@ -500,7 +500,11 @@ func copyBootJarsToPredefinedLocations(ctx android.ModuleContext, srcBootDexJars
 		dst := dstBootJarsByModule[name]
 
 		if src == nil {
-			ctx.ModuleErrorf("module %s does not provide a dex boot jar", name)
+			if !ctx.Config().AllowMissingDependencies() {
+				ctx.ModuleErrorf("module %s does not provide a dex boot jar", name)
+			} else {
+				ctx.AddMissingDependencies([]string{name})
+			}
 		} else if dst == nil {
 			ctx.ModuleErrorf("module %s is not part of the boot configuration", name)
 		} else {