message: use flto for cvodes
diff: @@ -60,10 +60,12 @@ CXX_MINOR := $(shell $(CXX) -dumpversion 2>&1 | cut -d'.' -f2)
  ifndef STAN_NO_COMPILER_OPTIMS
  ifeq (clang,$(CXX_TYPE))
  - CXXFLAGS_OPTIM ?= -fvectorize -ftree-vectorize -fslp-vectorize -ftree-slp-vectorize -fno-standalone-debug -fstrict-return -ftrigraphs -fvisibility=hidden -fvisibility-inlines-hidden
  + CXXFLAGS_OPTIM ?= -fvectorize -ftree-vectorize -fslp-vectorize -ftree-slp-vectorize -fno-standalone-debug -fstrict-return -fvisibility=hidden -fvisibility-inlines-hidden
  + CXXFLAGS_OPTIM_SUNDIALS ?= -fvectorize -ftree-vectorize -fslp-vectorize -ftree-slp-vectorize -fno-standalone-debug -fstrict-return -fvisibility=hidden -fvisibility-inlines-hidden
  ifeq ($(shell expr $(CXX_MAJOR) \>= 5), 1)
  CXXFLAGS_FLTO ?= -flto=full -fwhole-program-vtables -fstrict-vtable-pointers -fforce-emit-vtables
  - CXXFLAGS_FLTO ?= -flto=full -fwhole-program-vtables -fstrict-vtable-pointers -fforce-emit-vtables
  + CXXFLAGS_FLTO_SUNDIALS ?= -flto=full -fwhole-program-vtables -fstrict-vtable-pointers -fforce-emit-vtables
  + CXXFLAGS_OPTIM_SUNDIALS += $(CXXFLAGS_FLTO_SUNDIALS)
  endif
  endif
  ifeq (mingw32-g,$(CXX_TYPE))
  @@ -80,7 +82,7 @@ ifndef STAN_NO_COMPILER_OPTIMS
  CXXFLAGS_VERSION_OPTIM += -fsplit-loops
  ifneq ($(OS),Windows_NT)
  CXXFLAGS_FLTO ?= -flto -fuse-linker-plugin -fdevirtualize-at-ltrans
  - CXXFLAGS_FLTO_SUNDIALS ?= -flto -fuse-linker-plugin -fdevirtualize-at-ltrans
  + CXXFLAGS_OPTIM_SUNDIALS += -flto -fuse-linker-plugin -fdevirtualize-at-ltrans
  endif
  endif
  CXXFLAGS_OPTIM ?= $(CXXFLAGS_VERSION_OPTIM)
  