Don't pass deprecated -single_module linker flag on Darwin

man ld:
> -single_module
>     This is now the default so does not need to be specified.

Bug: 236924555
Test: m adb
Change-Id: If33a5c955deca4548c57703b232a3b9c0eaa3563

cc/library.go

@@ -925,7 +925,6 @@ func (library *libraryDecorator) linkerFlags(ctx ModuleContext, flags Flags) Fla
 		if ctx.Darwin() {
 			f = append(f,
 				"-dynamiclib",
-				"-single_module",
 				"-install_name @rpath/"+libName+flags.Toolchain.ShlibSuffix(),
 			)
 			if ctx.Arch().ArchType == android.X86 {