Fix the build with -no-undefined.

[orbea]

When building netcdf-cxx4 with sblitool (https://dev.midipix.org/cross/slibtool) it fails with many undefined references. This is because the build used -no-undefined which GNU libtool silently ignores while slibtool does not.

1. -lnetcdf should be in LIBADD and not LDADD. - Build log: netcdf-cxx4.rdlibtool.log
2. The global LDADD variable is unused and LDADD should be used for linking dependencies for programs, for example: foo_LDADD = bar.la. The global variable is LIBS, but it should just be removed instead since linking against yourself is wrong in this case.
3. libh5bzip2.la depends on hdf5 and the -lhdf5 linker flag is missing.

   
   rdlibtool --tag=CC --mode=link gcc -g -O2 -module -avoid-version -shared -export-dynamic -no-undefined -o libh5bzip2.la -rpath /usr/local/lib H5Zbzip2.lo blocksort.lo huffman.lo crctable.lo randtable.lo compress.lo decompress.lo bzlib.lo

rdlibtool: lconf: {.name="libtool"}. rdlibtool: fdcwd: {.fdcwd=AT_FDCWD, .realpath="/tmp/netcdf-cxx4/plugins"}. rdlibtool: lconf: fstatat(AT_FDCWD,".",...) = 0 {.st_dev = 45, .st_ino = 324927}. rdlibtool: lconf: openat(AT_FDCWD,"libtool",O_RDONLY,0) = -1 [ENOENT]. rdlibtool: lconf: openat(AT_FDCWD,"../",O_DIRECTORY,0) = 3. rdlibtool: lconf: fstat(3,...) = 0 {.st_dev = 45, .st_ino = 315376}. rdlibtool: lconf: openat(3,"libtool",O_RDONLY,0) = 4. rdlibtool: lconf: found "/tmp/netcdf-cxx4/libtool". rdlibtool: link: ln -s /dev/null .libs/libh5bzip2.a.disabled rdlibtool: link: gcc .libs/H5Zbzip2.o .libs/blocksort.o .libs/huffman.o .libs/crctable.o .libs/randtable.o .libs/compress.o .libs/decompress.o .libs/bzlib.o -g -O2 -shared -fPIC -Wl,--no-undefined -o .libs/libh5bzip2.so -Wl,--export-dynamic /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: .libs/H5Zbzip2.o: in function H5Z_filter_bzip2': /tmp/netcdf-cxx4/plugins/H5Zbzip2.c:204: undefined reference toH5free_memory' /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: /tmp/netcdf-cxx4/plugins/H5Zbzip2.c:212: undefined reference to `H5free_memory' collect2: error: ld returned 1 exit status rdlibtool: exec error upon slbt_exec_link_create_library(), line 1446: (see child process error messages). rdlibtool: < returned to > slbt_exec_link(), line 1868. make[1]: [Makefile:467: libh5bzip2.la] Error 2 make[1]: Leaving directory '/tmp/netcdf-cxx4/plugins' make: [Makefile:542: install-recursive] Error 1

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[orbea]

Also see this downstream issue. https://bugs.gentoo.org/778200

[WardF]

Thanks!

[orbea]

I updated this PR to correctly use LIBADD instead of LDFLAGS and to remove the incorrect and unused LDADD variable.

[WardF]

Thank you!