CMake: remove duplicated source file from list

Patch by Jack Howarth!

git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@210025 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/runtime/src/CMakeLists.txt b/runtime/src/CMakeLists.txt
index 3f0b853..dd29966 100644
--- a/runtime/src/CMakeLists.txt
+++ b/runtime/src/CMakeLists.txt
@@ -90,7 +90,6 @@
   kmp_ftn_extra.c
   kmp_global.c
   kmp_gsupport.c
-  kmp_global.c
   kmp_i18n.c
   kmp_io.c
   kmp_itt.c