parallel test race condition between ref_ctest/ref_ctest64 and ncdump_tst_output

[edhartnett]

When running tests in parallel (ctest -j N or make -j check), ncdump_tst_output intermittently fails, which then causes ncdump_tst_nccopy3 to fail as well.

The root cause is a file race condition. Both the standalone tests ref_ctest / ref_ctest64 and the shell script tst_output.sh write to ctest0.nc (and ctest0_64.nc) in the same build directory. With parallel execution, these can run concurrently, corrupting each other's output.

tst_output.sh calls ref_ctest internally and then runs ncgen -lc -o ctest0.nc, followed by a diff against a reference file. If the standalone ref_ctest test is simultaneously writing ctest0.nc, the diff or a subsequent step fails.

ncdump_tst_nccopy3 already declares a dependency on ncdump_tst_output, so it correctly waits — but when tst_output fails partway through, the files tst_nccopy3 needs (e.g. tst_output_c0tmp.nc) are never created, producing a "No such file or directory" error.

Observed CI output

 13/224 Test  #20: ncdump_tst_output .........................***Failed    0.86 sec
...
220/224 Test  #21: ncdump_tst_nccopy3 ........................***Failed    0.07 sec

*** Testing nccopy tst_output_c0tmp.nc nccopy3_copy_of_tst_output_c0tmp.nc ...
No such file or directory
Location: file ncdump/nccopy.c; fcn copy line 2011

Fix

Declare that tst_output depends on ref_ctest and ref_ctest64 in both build systems so they cannot run concurrently.

CMake (ncdump/CMakeLists.txt):

set_tests_properties(ncdump_tst_output PROPERTIES DEPENDS "ref_ctest;ref_ctest64")

Autotools (ncdump/Makefile.am):

# tst_output.sh runs ref_ctest and ref_ctest64 internally and
# writes to the same files (ctest0.nc, ctest0_64.nc).
tst_output.log: ref_ctest.log ref_ctest64.log