Switch to nano version of newlib (#5180)

* Switch to nano version of newlib

save about 50k of flash and 2k of RAM on Taranis

* Make nano optional, default=off and use bin_alloc for it

radio/src/CMakeLists.txt

@@ -41,6 +41,7 @@ option(TRACE_SIMPGMSPACE "Turn on traces in simpgmspace.cpp" ON)
 option(TRACE_LUA_INTERNALS "Turn on traces for Lua internals" OFF)
 option(BINDING_OPTIONS "Allow advanced frsky bindings" OFF)
 option(FRSKY_STICKS "Reverse sticks for FrSky sticks" OFF)
+option(NANO "Use nano newlib and binalloc")
 
 # since we reset all default CMAKE compiler flags for firmware builds, provide an alternate way for user to specify additional flags.
 set(FIRMWARE_C_FLAGS "" CACHE STRING "Additional flags for firmware target c compiler (note: all CMAKE_C_FLAGS[_*] are ignored for firmware/bootloader).")
@@ -467,7 +468,19 @@ if(NOT MSVC)
       add_definitions(-DSEMIHOSTING)
       set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --specs=rdimon.specs")
     endif()
+    # Use newlib nano, which saves a few kilobytes.
+    if(NOT NANO STREQUAL NO)
+      set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --specs=nano.specs")
+      if(NOT LUA STREQUAL NO)
+        # Lua needs %g and %f
+        set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -u _printf_float -u _scanf_float")
+      endif()
+      # Nano's malloc does work well with lua, use our own
+      add_definitions(-DUSE_BIN_ALLOCATOR)
+      set(SRC ${SRC} bin_allocator.cpp)
+    endif()
 
+    
     if(PCB STREQUAL X9D OR PCB STREQUAL X9D+ OR PCB STREQUAL X9E OR PCB STREQUAL X7 OR PCB STREQUAL X7S)
       add_subdirectory(targets/${TARGET_DIR}/bootloader)
       include_directories(${CMAKE_CURRENT_BINARY_DIR}/targets/${TARGET_DIR}/bootloader)