[Beignet] [PATCH] Fix GCC6 build bug

[Xiuli Pan]

From: Pan Xiuli <xiuli.pan at intel.com>

GCC6 refine the c headers and need to add the needed function header,
like the abs in math.h.

Signed-off-by: Pan Xiuli <xiuli.pan at intel.com>
---
 backend/src/backend/gen_insn_selection_optimize.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/backend/src/backend/gen_insn_selection_optimize.cpp b/backend/src/backend/gen_insn_selection_optimize.cpp
index 2ab2a7f..71333a4 100644
--- a/backend/src/backend/gen_insn_selection_optimize.cpp
+++ b/backend/src/backend/gen_insn_selection_optimize.cpp
@@ -9,6 +9,7 @@
 #include <algorithm>
 #include <climits>
 #include <map>
+#include <math.h>
 
 namespace gbe
 {
-- 
2.7.4