mk: add library common makefile support
mk: add library common makefile support

It is not always suitable to place the third party library source in
the optee-os directory, provide a common library makefile here, the
usage is similar as TA, the only difference is as follow:
TA Makefile:
BINARY :=  xxx
LIB Makefile:
LIBNAME := libxxx
And xxx.ta or libxxx.a is the target.

Reviewed-by: Jens Wiklander <7706914404370d7502c27a0eff493dcf491feb51@linaro.org>
Signed-off-by: Zeng Tao <ae5c7f8f383511cb075e5cee5f277c5f19ea314f@huawei.com>

matt2048/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os