message: turn off flto for windows
diff: @@ -77,7 +77,9 @@ ifndef STAN_NO_COMPILER_OPTIMS
  endif
  ifeq ($(shell expr $(CXX_MAJOR) \>= 7), 1)
  CXXFLAGS_VERSION_OPTIM += -fsplit-loops
  + ifeq ($(OS),Windows_NT)
  CXXFLAGS_FLTO ?= -flto -fuse-linker-plugin -fdevirtualize-at-ltrans
  + endif
  endif
  CXXFLAGS_OPTIM ?= $(CXXFLAGS_VERSION_OPTIM)
  CPPFLAGS_OPTIM ?= $(CXXFLAGS_OPTIM)
  