[gn build] Port c3f815b

Author: llvmgnsyncbot

llvm/utils/gn/secondary/llvm/unittests/Support/BUILD.gn

@@ -22,6 +22,7 @@ unittest("SupportTests") {
     "CRCTest.cpp",
     "CSKYAttributeParserTest.cpp",
     "CachePruningTest.cpp",
+    "Caching.cpp",
     "Casting.cpp",
     "CheckedArithmeticTest.cpp",
     "Chrono.cpp",