Fix makefile test against host os.

Change-Id: I7637845277012a189bf5f3598f9f0b1f599fbf75
diff --git a/build/Android.common_build.mk b/build/Android.common_build.mk
index 77f39c4..ee0cb09 100644
--- a/build/Android.common_build.mk
+++ b/build/Android.common_build.mk
@@ -40,7 +40,7 @@
   ART_BUILD_HOST_STATIC := false
 endif
 
-ifneq ($$(HOST_OS),linux)
+ifneq ($(HOST_OS),linux)
   ART_BUILD_HOST_STATIC := false
 endif