Set `LIBSYSCALL_SHIM_NOWRAPPER` for musl

Set `LIBSYSCALL_SHIM_NOWRAPPER` for musl

We need to set the LIBSYSCALL_SHIM_NOWRAPPER field in the configuration
file to prevent syscall shim layer from creating system call wrappers.
These wrappers are already defined in musl.

Signed-off-by: Dragos Iulian Argint <dragosargint21@gmail.com>
Reviewed-by: Sergiu Moga <sergiu.moga@protonmail.com>
Reviewed-by: Simon Kuenzer <simon@unikraft.io>
Approved-by: Simon Kuenzer <simon@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #5