Reduce modules exposed to Make in Mac builds

Device builds are no longer supported on Mac, but we do support building
various host tools, including the SDK build-tools and platform-tools
packages. These have dependencies on [java] device modules, so we don't
completely disable device modules, only hide them from Make (which makes
them more difficult to trigger from the command line).

Also fix the mac build of multiproduct_kati, so that `m blueprint_tools`
works on Mac.

Bug: 187222815
Test: `m`, `m dist`, etc on Mac
Change-Id: I92f16605d5cd173d431cbcb79081234d45cc6e2e

cmd/multiproduct_kati/main.go

@@ -166,15 +166,6 @@ type mpContext struct {
 	MainLogsDir string
 }
 
-func detectTotalRAM() uint64 {
-	var info syscall.Sysinfo_t
-	err := syscall.Sysinfo(&info)
-	if err != nil {
-		panic(err)
-	}
-	return info.Totalram * uint64(info.Unit)
-}
-
 func findNamedProducts(soongUi string, log logger.Logger) []string {
 	cmd := exec.Command(soongUi, "--dumpvars-mode", "--vars=all_named_products")
 	output, err := cmd.Output()