MMTk PR broke Makefile target used to retrieve all deps

[d-netto]

We fetch the tarball with all dependencies' sources in our build.

The MMTk PR apparently broke that.

Running make -C deps getall on a x86_64 Linux machine gives me:

...
make: *** No rule to make target 'get-mmtk_julia', needed by 'getall'.  Stop.
make: Leaving directory '/home/ubuntu/julia-RAI/deps'

[d-netto]

(Thanks @rbvermaa for investigating this).

[inkydragon]

julia/deps/mmtk_julia.mk

Line 27 in d3964b6

get-mmtk_julia: $(MMTK_JULIA_SRC_FILE)

$ make -j -C deps getall
make: Entering directory '/mnt/d/jl/julia/deps'
make: *** No rule to make target 'get-mmtk_julia', needed by 'getall'.  Stop.
make: Leaving directory '/mnt/d/jl/julia/deps'
$ make -C deps get-mmtk_julia
make: Entering directory '/mnt/d/jl/julia/deps'
make: *** No rule to make target 'get-mmtk_julia'.  Stop.
make: Leaving directory '/mnt/d/jl/julia/deps'
$ make -C deps print-MMTK_JULIA_SRC_FILE
make: Entering directory '/mnt/d/jl/julia/deps'
MMTK_JULIA_SRC_FILE=
make: Leaving directory '/mnt/d/jl/julia/deps'

So MMTK_JULIA_SRC_FILE is not defined.