[libc][newlib]在不开启libc的情况下，依然定义RT_USING_NEWLIB和数学库
[libc][newlib]在不开启libc的情况下，依然定义RT_USING_NEWLIB和数学库

nongxiaoming/rt-thread,hezlog/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,nongxiaoming/rt-thread,nongxiaoming/rt-thread,hezlog/rt-thread,RT-Thread/rt-thread,hezlog/rt-thread,RT-Thread/rt-thread,hezlog/rt-thread,geniusgogo/rt-thread,geniusgogo/rt-thread,geniusgogo/rt-thread,geniusgogo/rt-thread,nongxiaoming/rt-thread,hezlog/rt-thread,geniusgogo/rt-thread,hezlog/rt-thread,RT-Thread/rt-thread,hezlog/rt-thread,RT-Thread/rt-thread,nongxiaoming/rt-thread,geniusgogo/rt-thread,geniusgogo/rt-thread,nongxiaoming/rt-thread,nongxiaoming/rt-thread,RT-Thread/rt-thread