[SystemZ] Add to --enable-targets=all

This patch finally enables the SystemZ target in the default build
(with --enable-targets=all).

Patch by Richard Sandiford.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181209 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 77b3436..fffdf9b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -84,6 +84,7 @@
   NVPTX
   PowerPC
   Sparc
+  SystemZ
   X86
   XCore
   )