Fix ALLOW_MISSING_DEPENDENCIES=true builds

Don't error out immediately if a SourceDepTag dependency is missing
if ALLOW_MISSING_DEPENDENCIES=true is set.

Test: forrest on unbundled build
Change-Id: I9077013e09e3ad0e90ae5163b26aace5b263e63a
diff --git a/android/module.go b/android/module.go
index 64fbdac..c1f3e79 100644
--- a/android/module.go
+++ b/android/module.go
@@ -1441,7 +1441,11 @@
 		if m := SrcIsModule(e); m != "" {
 			module := ctx.GetDirectDepWithTag(m, SourceDepTag)
 			if module == nil {
-				ctx.ModuleErrorf(`missing dependency on %q, is the property annotated with android:"path"?`, m)
+				if ctx.Config().AllowMissingDependencies() {
+					ctx.AddMissingDependencies([]string{m})
+				} else {
+					ctx.ModuleErrorf(`missing dependency on %q, is the property annotated with android:"path"?`, m)
+				}
 				continue
 			}
 			if srcProducer, ok := module.(SourceFileProducer); ok {
@@ -1458,7 +1462,11 @@
 		if m := SrcIsModule(s); m != "" {
 			module := ctx.GetDirectDepWithTag(m, SourceDepTag)
 			if module == nil {
-				ctx.ModuleErrorf(`missing dependency on %q, is the property annotated with android:"path"?`, m)
+				if ctx.Config().AllowMissingDependencies() {
+					ctx.AddMissingDependencies([]string{m})
+				} else {
+					ctx.ModuleErrorf(`missing dependency on %q, is the property annotated with android:"path"?`, m)
+				}
 				continue
 			}
 			if srcProducer, ok := module.(SourceFileProducer); ok {