Fix modernize-use-using warning reported by clang-tidy

.clang-tidy

@@ -1,7 +1,7 @@
 # refer to https://clang.llvm.org/extra/clang-tidy/checks/list.html
 Checks: -*, clang-analyzer-core.*, clang-analyzer-cplusplus.*, clang-analyzer-deadcode.*, clang-analyzer-nullability.*, clang-analyzer-security.*, clang-analyzer-unix.*, clang-analyzer-valist.*, cppcoreguidelines-init-variables, cppcoreguidelines-macro-usage, cppcoreguidelines-interfaces-global-init, cppcoreguidelines-narrowing-conversions, cppcoreguidelines-no-malloc, cppcoreguidelines-prefer-member-initializer, cppcoreguidelines-special-member-functions, cppcoreguidelines-slicing, google-build-explicit-make-pair, google-default-arguments, google-explicit-constructor, modernize-avoid-bind, modernize-loop-convert, modernize-macro-to-enum, modernize-make-shared, modernize-make-unique, modernize-pass-by-value, modernize-redundant-void-arg, modernize-return-braced-init-list, modernize-use-auto, modernize-use-bool-literals, modernize-use-emplace, modernize-use-equals-default, modernize-use-equals-delete, modernize-use-nullptr, modernize-use-override, modernize-use-using, performance-faster-string-find, performance-for-range-copy, performance-implicit-conversion-in-loop, performance-inefficient-algorithm, performance-inefficient-vector-operation, performance-move-const-arg, performance-move-constructor-init, performance-no-automatic-move, performance-trivially-destructible, performance-type-promotion-in-math-fn, performance-unnecessary-copy-initialization, performance-unnecessary-value-param
 
-WarningsAsErrors: clang-analyzer-*, -clang-analyzer-security.insecureAPI.rand, cppcoreguidelines-interfaces-global-init, cppcoreguidelines-no-malloc, cppcoreguidelines-slicing, google-*, modernize-use-emplace, modernize-use-equals-default, modernize-use-equals-delete, performance-implicit-conversion-in-loop, performance-inefficient-algorithm, performance-move-constructor-init, performance-no-automatic-move, performance-trivially-destructible, performance-type-promotion-in-math-fn, performance-unnecessary-copy-initialization
+WarningsAsErrors: clang-analyzer-*, -clang-analyzer-security.insecureAPI.rand, cppcoreguidelines-interfaces-global-init, cppcoreguidelines-no-malloc, cppcoreguidelines-slicing, google-*, modernize-use-emplace, modernize-use-equals-default, modernize-use-equals-delete, performance-implicit-conversion-in-loop, performance-inefficient-algorithm, performance-move-constructor-init, performance-no-automatic-move, performance-trivially-destructible, performance-type-promotion-in-math-fn, performance-unnecessary-copy-initialization, modernize-use-using
 
 CheckOptions:
   - key:           cppcoreguidelines-special-member-functions.AllowSoleDefaultDtor

src/common/sha1.cc

@@ -79,10 +79,10 @@ A million repetitions of "a"
 
 void SHA1Transform(uint32_t state[5], const unsigned char buffer[64]) {
   uint32_t a, b, c, d, e;
-  typedef union {
+  using CHAR64LONG16 = union {
     unsigned char c[64];
     uint32_t l[16];
-  } CHAR64LONG16;
+  };
 #ifdef SHA1HANDSOFF
   CHAR64LONG16 block[1]; /* use array to appear as a pointer */
   memcpy(block, buffer, 64);