Disable libbrillo-http and libbrillo-stream on mac.

These libraries don't compile on mac, so we will disable them for now.

Bug: 24619596
TEST=`mmma external/libbrillo` on mac

Change-Id: I4dc408f0b39308404fe2687c53d3deaceb3c5097
diff --git a/Android.mk b/Android.mk
index ab50d46..1d222cd 100644
--- a/Android.mk
+++ b/Android.mk
@@ -313,7 +313,9 @@
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)
 include $(BUILD_HOST_SHARED_LIBRARY)
 
-# Shared stream library for target
+ifeq ($(HOST_OS),linux)
+
+# Shared stream library for host
 # ========================================================
 include $(CLEAR_VARS)
 LOCAL_CPP_EXTENSION := $(libbrillo_cpp_extension)
@@ -329,7 +331,7 @@
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)
 include $(BUILD_HOST_SHARED_LIBRARY)
 
-# Shared http library for target
+# Shared http library for host
 # ========================================================
 include $(CLEAR_VARS)
 LOCAL_CPP_EXTENSION := $(libbrillo_cpp_extension)
@@ -345,6 +347,8 @@
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)
 include $(BUILD_HOST_SHARED_LIBRARY)
 
+endif  # HOST_OS == linux
+
 # Unit tests.
 # ========================================================
 include $(CLEAR_VARS)