Add _<OS> suffix support, remove USE_MINGW

USE_MINGW is no longer supported by Make

Change-Id: I399190ac9e92a2e633bf5438d8deb653beae1bb1

androidmk/cmd/androidmk/android.go

@@ -381,6 +381,9 @@ var propertyPrefixes = []struct{ mk, bp string }{
 	{"32", "multilib.lib32"},
 	// 64 must be after x86_64
 	{"64", "multilib.lib64"},
+	{"darwin", "target.darwin"},
+	{"linux", "target.linux"},
+	{"windows", "target.windows"},
 }
 
 var conditionalTranslations = map[string]map[bool]string{
@@ -414,9 +417,6 @@ var conditionalTranslations = map[string]map[bool]string{
 	"($(BUILD_OS), linux)": {
 		true:  "target.linux",
 		false: "target.not_linux"},
-	"USE_MINGW": {
-		true:  "target.windows",
-		false: "target.not_windows"},
 	"(,$(TARGET_BUILD_APPS))": {
 		false: "product_variables.unbundled_build",
 	},

androidmk/cmd/androidmk/test.go

@@ -240,6 +240,31 @@ include $(BUILD_SHARED_LIBRARY)
 cc_library_shared {
     logtags: ["events.logtags"] + ["events2.logtags"],
 }
+`,
+	},
+	{
+		desc: "_<OS> suffixes",
+		in: `
+include $(CLEAR_VARS)
+LOCAL_SRC_FILES_darwin := darwin.c
+LOCAL_SRC_FILES_linux := linux.c
+LOCAL_SRC_FILES_windows := windows.c
+include $(BUILD_SHARED_LIBRARY)
+`,
+		expected: `
+cc_library_shared {
+    target: {
+        darwin: {
+            srcs: ["darwin.c"],
+        },
+        linux: {
+            srcs: ["linux.c"],
+        },
+        windows: {
+            srcs: ["windows.c"],
+        },
+    },
+}
 `,
 	},
 }