musl: Create symlinks for stub libraries

musl: Create symlinks for stub libraries

Some libraries e.g. libm.so are needed to be
created so that SDKs built with distros which
disable static librararies can have the stubs
and since default linker script requires -lm
this helps in compiling applications with SDK

there are .a equivalents for these libraries
but they do not land in SDKs when static libs
are disabled distrowide

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster@mvista.com>