qualify location of libccalltest

[tkelman]

fixes Base.runtests("ccall") when run from a different directory, since the cd in test/runtests.jl was removed by #8745

Either the cd needs to go back or we can merge this pr:

     * ccall               exception on 1: ERROR: LoadError: error compiling anonymous: could not load library './libccalltest'
./libccalltest: cannot open shared object file: No such file or directory
 in include at ./boot.jl:254
 in include_from_node1 at ./loading.jl:187
 in runtests at /home/tkelman/Julia/julia-4b757af634/share/julia/test/testdefs.jl:197
 in anonymous at /home/tkelman/Julia/julia-4b757af634/share/julia/test/runtests.jl:14
 in anonymous at multi.jl:623
 in run_work_thunk at multi.jl:584
 in remotecall_fetch at multi.jl:657
 in remotecall_fetch at multi.jl:672
 in anonymous at task.jl:1392
while loading /home/tkelman/Julia/julia-4b757af634/share/julia/test/ccall.jl, in expression starting on line 5
ERROR: LoadError: LoadError: error compiling anonymous: could not load library './libccalltest'
./libccalltest: cannot open shared object file: No such file or directory
 in include at ./boot.jl:254
 in include_from_node1 at ./loading.jl:187
 in runtests at /home/tkelman/Julia/julia-4b757af634/share/julia/test/testdefs.jl:197
 in anonymous at /home/tkelman/Julia/julia-4b757af634/share/julia/test/runtests.jl:14
 in anonymous at multi.jl:623
 in run_work_thunk at multi.jl:584
 in remotecall_fetch at multi.jl:657
 in remotecall_fetch at multi.jl:672
 in anonymous at task.jl:1392
while loading /home/tkelman/Julia/julia-4b757af634/share/julia/test/ccall.jl, in expression starting on line 5
while loading /home/tkelman/Julia/julia-4b757af634/share/julia/test/runtests.jl, in expression starting on line 14
ERROR: A test has failed. Please submit a bug report (https://github.com/JuliaLang/julia/issues)
including error messages above and the output of versioninfo():
Julia Version 0.4.0-dev+6075
Commit 4b757af (2015-07-19 00:53 UTC)
Platform Info:
  System: Linux (x86_64-unknown-linux-gnu)
  CPU: Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Penryn)
  LAPACK: libopenblas
  LIBM: libopenlibm
  LLVM: libLLVM-3.3

 in error at ./error.jl:21
 in runtests at interactiveutil.jl:406
 in runtests at interactiveutil.jl:395

[tkelman]

Probably worth a separate issue, but Base.runtests("all", 2) is broken since #8745 as well. Tried changing @everywhere include("testdefs.jl") to @everywhere include(joinpath(dirname(@__FILE__), "testdefs.jl")) in test/runtests.jl but that doesn't seem to fix it.

[tkelman]

@vtjnash any objections here?