message: fix missing exe in  bin/windows-stanc copy
diff: @@ -44,7 +44,7 @@ bin/stanc$(EXE) : $(shell find $(STANC3)/src/ -type f -name '*.ml*') $(STANC#)
  else ifneq (,$(wildcard bin/$(OS_TAG)-stanc))
  bin/stanc$(EXE) :
  cp bin/$(OS_TAG)-stanc bin/stanc$(EXE)
  - chmod +x bin/stanc
  + chmod +x bin/stanc$(EXE)
  else ifeq ($(OS_TAG),windows)
  bin/stanc$(EXE) :
  @@ -53,8 +53,8 @@ bin/stanc$(EXE) :
  else
  bin/stanc$(EXE) :
  @mkdir -p $(dir $@)
  - curl -L https://github.com/stan-dev/stanc3/releases/download/nightly/$(OS_TAG)-stanc -o bin/stanc
  - chmod +x bin/stanc
  + curl -L https://github.com/stan-dev/stanc3/releases/download/nightly/$(OS_TAG)-stanc -o bin/stanc$(EXE)
  + chmod +x bin/stanc$(EXE)
  endif
  # libstanc build rules
  