ART: Increase command buffer size in assembler_thumb_test

Change-Id: I5fe0014a2928772650bdb120a877eb9624bf7651
diff --git a/compiler/utils/assembler_thumb_test.cc b/compiler/utils/assembler_thumb_test.cc
index 534783a..3312f8f 100644
--- a/compiler/utils/assembler_thumb_test.cc
+++ b/compiler/utils/assembler_thumb_test.cc
@@ -171,7 +171,7 @@
   }
   out.close();
 
-  char cmd[256];
+  char cmd[1024];
 
   // Assemble the .S
   snprintf(cmd, sizeof(cmd), "%s%sas %s -o %s.o", toolsdir.c_str(), TOOL_PREFIX, filename, filename);