Don't check apex_available for host

The check doesn't make sense for host.

Test: ALLOW_MISSING_DEPENDENCIES=true DIST_DIR=out/dist
./art/tools/dist_linux_bionic.sh -j110 com.android.art.host
is successful

Change-Id: Icdb4bb557a83b3c8044e6c73721dab47c56888a1
diff --git a/apex/apex.go b/apex/apex.go
index 000792a..8b2dcbe 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -1191,11 +1191,13 @@
 	})
 
 	// check apex_available requirements
-	for _, fi := range filesInfo {
-		if am, ok := fi.module.(android.ApexModule); ok {
-			if !am.AvailableFor(ctx.ModuleName()) {
-				ctx.ModuleErrorf("requires %q that is not available for the APEX", fi.module.Name())
-				return
+	if !ctx.Host() {
+		for _, fi := range filesInfo {
+			if am, ok := fi.module.(android.ApexModule); ok {
+				if !am.AvailableFor(ctx.ModuleName()) {
+					ctx.ModuleErrorf("requires %q that is not available for the APEX", fi.module.Name())
+					return
+				}
 			}
 		}
 	}