[Analysis] 'static' function 'shortenFileName' should be declared 'static inline' (NFC)

llvm-project/llvm/include/llvm/Analysis/DOTGraphTraitsPass.h:89:13:
 error: 'static' function 'shortenFileName' declared in header file should be declared 'static inline' [-Werror,-Wunneeded-internal-declaration]
  static void shortenFileName(std::string &FN, unsigned char len = 250) {