Fix Makefile so that it does not mis-show ARCH as 86_64 when building on 32-bit Win.

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@8238 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/Makefile

@@ -58,13 +58,14 @@ endif
 # Architecture #
 ################
 
-# To build on AMD64 or Itanium machines, ARCH should be set.
-# We attempt to auto-detect this here.
-ifneq (,$(findstring 86_64, $(shell uname -m)))
-	ARCH = amd64
-endif
-ifneq (,$(findstring ia64, $(shell uname -m)))
-	ARCH = ia64
+# For Linux, we use uname to see if we are on a 64-bit (AMD64 or Itanium) machine
+ifeq ($(OSTYPE),linux)
+	ifneq (,$(findstring 86_64, $(shell uname -m)))
+		ARCH = amd64
+	endif
+	ifneq (,$(findstring ia64, $(shell uname -m)))
+		ARCH = ia64
+	endif
 endif
 # For Mac/Windows, we decide whether to build in 64-bit mode based on
 # whether java is 32/64-bit (since these need to match)