Disable building libdiskconfig on non-Linux hosts

libdiskconfig depends deeply on some Linux-specific things like
/usr/include/linux/fs.h which don't exist on other OSes. Disable
building the host library for those platforms.

Change-Id: Ibccdfaa65be788f049ea3c1500f884c8d541e60b
diff --git a/libdiskconfig/Android.mk b/libdiskconfig/Android.mk
index ef08bec..c887955 100644
--- a/libdiskconfig/Android.mk
+++ b/libdiskconfig/Android.mk
@@ -3,7 +3,6 @@
 
 ifneq ($(TARGET_SIMULATOR),true)
 
-
 commonSources := \
 	diskconfig.c \
 	diskutils.c \
@@ -16,13 +15,13 @@
 LOCAL_SYSTEM_SHARED_LIBRARIES := libcutils liblog libc
 include $(BUILD_SHARED_LIBRARY)
 
+ifeq ($(HOST_OS),linux)
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := $(commonSources)
 LOCAL_MODULE := libdiskconfig_host
 LOCAL_SYSTEM_SHARED_LIBRARIES := libcutils
 LOCAL_CFLAGS := -O2 -g -W -Wall -Werror -D_LARGEFILE64_SOURCE
 include $(BUILD_HOST_STATIC_LIBRARY)
-
-
+endif # HOST_OS == linux
 
 endif  # ! TARGET_SIMULATOR