NetCDF 4.10.1 test unit_test/run_dfaltpluginpath.sh fails if HOME is not set

[Alexander-Barth]

In Julia, we are building NetCDF in a sand-boxed environment where HOME is not defined.
I am currently trying to make a build with plugins enabled, and but the test run_dfaltpluginpath.sh fails:

/unit_test # ./run_dfaltpluginpath.sh
Segmentation fault (core dumped)

The test tries to run the utility ncpathcvt with the argument:

# /workspace/srcdir/netcdf-c-4.10.1/unit_test/../ncdump/ncpathcvt '-S;' -w '/tmp;'
Segmentation fault (core dumped)

After /tmp; there should come the HOME directory. Setting HOME to a dummy value, like /home/dummy works for run_dfaltpluginpath.sh.

gdb suggested that the segmentation fault triggered in nclistclearall:

sandbox:${WORKSPACE}/srcdir/netcdf-c-4.10.1/unit_test # gdb --args /workspace/srcdir/netcdf-c-4.10.1/ncdump/.libs/lt-ncpathcvt '-S;' -w '/tmp;'
[...]
Starting program: /workspace/srcdir/netcdf-c-4.10.1/ncdump/.libs/lt-ncpathcvt -S\; -w /tmp\;
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7e10d84 in nclistclearall () from /workspace/srcdir/netcdf-c-4.10.1/liblib/.libs/libnetcdf.so.22
(gdb) where
#0  0x00007ffff7e10d84 in nclistclearall () from /workspace/srcdir/netcdf-c-4.10.1/liblib/.libs/libnetcdf.so.22
#1  0x00007ffff7e10d58 in nclistfreeall () from /workspace/srcdir/netcdf-c-4.10.1/liblib/.libs/libnetcdf.so.22
#2  0x00007ffff7e0ec48 in ncuriparse () from /workspace/srcdir/netcdf-c-4.10.1/liblib/.libs/libnetcdf.so.22
#3  0x00007ffff7e185b6 in testurl () from /workspace/srcdir/netcdf-c-4.10.1/liblib/.libs/libnetcdf.so.22
#4  0x00007ffff7e17d4b in NCpathcvt () from /workspace/srcdir/netcdf-c-4.10.1/liblib/.libs/libnetcdf.so.22
#5  0x00007ffff7e18295 in NCpathcvt_test () from /workspace/srcdir/netcdf-c-4.10.1/liblib/.libs/libnetcdf.so.22
#6  0x00000000004016f8 in processdir ()
#7  0x0000000000401b5e in main ()

I guess it is fine for the tests to set a dummy HOME variable, but I wanted to let you since apparently the failure is in nclistclearall from libnetcdf.so.

CC: @eschnett @bjarthur