[gn build] Port 8dc7db7

Author: llvmgnsyncbot

llvm/utils/gn/secondary/clang-tools-extra/clang-tidy/readability/BUILD.gn

@@ -35,6 +35,7 @@ static_library("readability") {
     "IsolateDeclarationCheck.cpp",
     "MagicNumbersCheck.cpp",
     "MakeMemberFunctionConstCheck.cpp",
+    "MathMissingParenthesesCheck.cpp",
     "MisleadingIndentationCheck.cpp",
     "MisplacedArrayIndexCheck.cpp",
     "NamedParameterCheck.cpp",