RFR (XS): use os.name property to identify Windows OS

[Christian Thalinger]

diff --git a/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotVMConfig.java b/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotVMConfig.java
--- a/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotVMConfig.java
+++ b/graal/com.oracle.graal.hotspot/src/com/oracle/graal/hotspot/HotSpotVMConfig.java
@@ -34,7 +34,7 @@
 
     // os information, register layout, code generation, ...
     public boolean cAssertions;
-    public boolean windowsOs;
+    public final boolean windowsOs = System.getProperty("os.name", "").startsWith("Windows");
     public int codeEntryAlignment;
     public boolean verifyOops;
     public boolean ciTime;
diff --git a/src/share/vm/graal/graalCompilerToVM.cpp b/src/share/vm/graal/graalCompilerToVM.cpp
--- a/src/share/vm/graal/graalCompilerToVM.cpp
+++ b/src/share/vm/graal/graalCompilerToVM.cpp
@@ -629,11 +643,7 @@
 #define set_int_array(name, value) do { env->SetObjectField(config, getFieldID(env, config, name, "[I"), value); } while (0)
 
   guarantee(HeapWordSize == sizeof(char*), "Graal assumption that HeadWordSize == machine word size is wrong");
-#ifdef _WIN64
-  set_boolean("windowsOs", true);
-#else
-  set_boolean("windowsOs", false);
-#endif
+
   set_boolean("cAssertions", DEBUG_ONLY(true) NOT_DEBUG(false));
   set_boolean("verifyOops", VerifyOops);
   set_boolean("ciTime", CITime);