gcc :how to specify architecture?

问题

How can I specify architecture when I build a library?
I need to build a library in armeabi-v7a for an Android project.
I found -march option, so this is my command :

$ gcc -shared -o liballnet.so -fPIC *.c -march=armv7-a

But it doesn't work :

error: unknown target CPU 'armv7-a'

Any ideas?

来源：https://stackoverflow.com/questions/45805322/gcc-how-to-specify-architecture