[runtime] Fix include guard in Runtime/CMakeConfig.h. (#21227)

Greg Parker · web-flow · commit b875dca8ba15 · 2018-12-14T13:29:10.000-08:00
diff --git a/include/swift/Runtime/CMakeConfig.h.in b/include/swift/Runtime/CMakeConfig.h.in
@@ -2,6 +2,7 @@
 // See https://cmake.org/cmake/help/v3.0/command/configure_file.html.
 
 #ifndef SWIFT_RUNTIME_CMAKECONFIG_H
+#define SWIFT_RUNTIME_CMAKECONFIG_H
 
 #cmakedefine01 SWIFT_DARWIN_ENABLE_STABLE_ABI_BIT
 
