message: abseil use master branch
diff: @@ -39,8 +39,8 @@ else (systemlib_ABSEIL_CPP)
  include (ExternalProject)
  set(abseil_cpp_INCLUDE_DIR ${CMAKE_BINARY_DIR}/abseil_cpp/src/abseil_cpp_build)
  - set(abseil_cpp_URL https://github.com/abseil/abseil-cpp/archive/e01d95528ea2137a4a27a88d1f57c6cb260aafed.tar.gz)
  - set(abseil_cpp_HASH SHA256=84043ed402d2a2a6ba4cdddb7e85118b1158fd81fe4ac3a14adc343d054c1e2e)
  + set(abseil_cpp_URL https://github.com/abseil/abseil-cpp.git)
  + set(abseil_cpp_TAG master)
  set(abseil_cpp_BUILD ${CMAKE_BINARY_DIR}/abseil_cpp/src/abseil_cpp_build)
  if(WIN32)
  @@ -48,7 +48,7 @@ else (systemlib_ABSEIL_CPP)
  set(abseil_cpp_STATIC_LIBRARIES
  ${abseil_cpp_BUILD}/absl/base/Release/absl_base.lib
  ${abseil_cpp_BUILD}/absl/base/Release/absl_dynamic_annotations.lib
  - ${abseil_cpp_BUILD}/absl/base/Release/absl_malloc_internal.lib
  + ${abseil_cpp_BUILD}/absl/base/Release/absl_internal_malloc_internal.lib
  ${abseil_cpp_BUILD}/absl/strings/Release/absl_strings.lib
  ${abseil_cpp_BUILD}/absl/strings/Release/str_format_internal.lib
  ${abseil_cpp_BUILD}/absl/types/Release/absl_bad_optional_access.lib)
  @@ -79,8 +79,7 @@ else (systemlib_ABSEIL_CPP)
  ExternalProject_Add(abseil_cpp_build
  PREFIX abseil_cpp
  - URL ${abseil_cpp_URL}
  - URL_HASH ${abseil_cpp_HASH}
  + GIT_REPOSITORY ${abseil_cpp_URL}
  DOWNLOAD_DIR "${DOWNLOAD_LOCATION}"
  BUILD_IN_SOURCE 1
  BUILD_BYPRODUCTS ${abseil_cpp_STATIC_LIBRARIES}
  