[version] bump gdb to 7.7
diff --git a/toolvers b/toolvers
index 3846170..117493e 100644
--- a/toolvers
+++ b/toolvers
@@ -1,6 +1,6 @@
 GCCVER=4.8.2
 BINVER=2.24
-GDBVER=7.6.2
+GDBVER=7.7
 GMPVER=5.1.3
 MPCVER=1.0.2
 MPFRVER=3.1.2