Fixed targets ti be x86_64, important note: have not tested this on linux machine

lib/spack/spack/architectures/linux.py

@@ -3,9 +3,9 @@
 
 class Linux(Architecture):
     priority    = 60
-    front_end   = 'linux'
-    back_end    = 'linux'
-    default     = 'linux'
+    front_end   = 'x86_64'
+    back_end    = 'x86_64'
+    default     = 'x86_64'
 
     def __init__(self):
         super(Linux, self).__init__('linux')
@@ -15,4 +15,4 @@ def __init__(self):
     def detect(self):
         arch = subprocess.Popen(['uname', '-i'], stdout = subprocess.PIPE)
         arch, _ = arch.communicate()
-        return 'x86_64' in arch.strip()
+        return 'linux' in arch.strip().lower()