libgo: remove go-memcmp.c in cmake file

go-memcmp.c is removed in CL 183537.

Change-Id: I2826fa020602be90fb7282740c8357e14d4e882a
Reviewed-on: https://go-review.googlesource.com/c/gollvm/+/183622
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/libgo/CMakeLists.txt b/libgo/CMakeLists.txt
index f47ede2..1bdd7d6 100644
--- a/libgo/CMakeLists.txt
+++ b/libgo/CMakeLists.txt
@@ -402,7 +402,6 @@
   "runtime/go-fieldtrack.c"
   "runtime/go-matherr.c"
   "runtime/go-memclr.c"
-  "runtime/go-memcmp.c"
   "runtime/go-memequal.c"
   "runtime/go-nanotime.c"
   "runtime/go-now.c"