'vendor_available: *' will not create product variant

With this patch, `vendor_available: true` will no longer creates
product variant. Instead, modules need to set `product_available:
true` if they have to be available to product vanriant.
If both properties are defined for VNDKs, they must have the same
values.

Bug: 150902910
Test: m nothing
Change-Id: I28fb6886e6114583227a31151136627c8516ac9c

cc/compiler.go

@@ -479,8 +479,7 @@ func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags, deps
 	}
 
 	if ctx.inProduct() {
-		// TODO(b/150902910): must use 'compiler.Properties.Target.Product.Cflags'
-		flags.Local.CFlags = append(flags.Local.CFlags, esc(compiler.Properties.Target.Vendor.Cflags)...)
+		flags.Local.CFlags = append(flags.Local.CFlags, esc(compiler.Properties.Target.Product.Cflags)...)
 	}
 
 	if ctx.inRecovery() {