Remove unknown rules from .PHONY.
Make 'all' be the default target for jerryscript and execute `all` target.
This way no definition order issue could happen in the future.
Do not include Makefile.base as 'DIRS' are not used here.
Also if 'all' target was to be used, there would be two rules creating
`$(BINDIR)/jerryscript.a`.
By default `Makefile.jerryscript` executes `libjerry` as it is the first
target.
Without this disabled `nanosleep()` is used, which isn't provided for
most our platforms (though the header `<time.h>` is).
Furthermore, that macro is only used in that instance throughout the
JerryScript codebase.
