Add statements to generate a sys/syscall.mk file for inclusion during the libc/libc_r to automatically pick up syscall names on the assumption that default asm code needs to generated for them.
Add statements to generate a sys/syscall.mk file for inclusion
during the libc/libc_r to automatically pick up syscall names on
the assumption that default asm code needs to generated for them.

In the up-coming changes to the libc makefiles, there is the option
to provide a machine dependent asm source file which will turn off
the automatic generation of the default. There is also an option
to just stop code being generated for a syscall. In most cases,
though, the default asm code is all that is required, so this
change makes that the most convenient was to do business.

Idea suggested by: bde

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