Julia: Latest master won't compile with JULIA_ENABLE_THREADING off

[tshort]

With JULIA_ENABLE_THREADING turned off, compiling fails with the following error:

    LINK usr/lib/libjulia.so.1.3
/sbin/ld: ./threading.o: in function `jl_threading_run':
/home/tshort/tmp/julia/src/threading.c:510: undefined reference to `sleep_lock'
/sbin/ld: /home/tshort/tmp/julia/src/threading.c:511: undefined reference to `sleep_alarm'
/sbin/ld: /home/tshort/tmp/julia/src/threading.c:517: undefined reference to `sleep_lock'
/sbin/ld: /home/tshort/tmp/julia/src/threading.c:518: undefined reference to `sleep_alarm'
/sbin/ld: ./gc.o: in function `mark_roots':
/home/tshort/tmp/julia/src/gc.c:2502: undefined reference to `jl_gc_mark_enqueued_tasks'
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:299: /home/tshort/tmp/julia/usr/lib/libjulia.so.1.3] Error 1
make: *** [Makefile:75: julia-src-release] Error 2

[JeffBezanson]

Embrace the multithreaded future! :stuck_out_tongue:

[tshort]

I tried a couple of easy fixes here. This branch compiles and builds the system image, but then it segfaults as follows. I'm not sure how to debug that.

Total ───────  94.141273 seconds 
Base: ───────  31.995914 seconds 33.9871%
Stdlibs: ────  62.142596 seconds 66.0099%
    JULIA usr/lib/julia/sys-o.a
Generating precompile statements...
signal (11): Segmentation fault
in expression starting at /home/tshort/tmp/julia/contrib/generate_precompile.jl:8
unknown function (ip: 0xffffffffffffffff)
uv_write at ./stream.jl:883
_ZL16incomplete_fname at /home/tshort/tmp/julia/usr/bin/../lib/libjulia.so.1 (unknown line)
Allocations: 4672558 (Pool: 4670913; Big: 1645); GC: 9
/bin/sh: line 1: 11424 Segmentation fault      (core dumped) /home/tshort/tmp/julia/usr/bin/julia -O3 -C "native" --output-o /home/tshort/tmp/julia/usr/lib/julia/sys-o.a.tmp --startup-file=no --warn-overwrite=yes --sysimage /home/tshort/tmp/julia/usr/lib/julia/sys.ji /home/tshort/tmp/julia/contrib/generate_precompile.jl 1
*** This error is usually fixed by running `make clean`. If the error persists, try `make cleanall`. ***
make[1]: *** [sysimage.mk:85: /home/tshort/tmp/julia/usr/lib/julia/sys-o.a] Error 1
make: *** [Makefile:84: julia-sysimg-release] Error 2