Support musl builds in Make

Rewrite linux_musl to linux when exporting to Make.

Bug: 190084016
Test: m USE_HOST_MUSL=true adb
Change-Id: I48eed5bd7380a07c5106a9b2bd96899fb58f7a7f
diff --git a/apex/androidmk.go b/apex/androidmk.go
index ebf0833..2f10904 100644
--- a/apex/androidmk.go
+++ b/apex/androidmk.go
@@ -212,7 +212,7 @@
 			}
 			if host {
 				makeOs := fi.module.Target().Os.String()
-				if fi.module.Target().Os == android.Linux || fi.module.Target().Os == android.LinuxBionic {
+				if fi.module.Target().Os == android.Linux || fi.module.Target().Os == android.LinuxBionic || fi.module.Target().Os == android.LinuxMusl {
 					makeOs = "linux"
 				}
 				fmt.Fprintln(w, "LOCAL_MODULE_HOST_OS :=", makeOs)