Duplicate symbols on OSX in autotools-based build.

[WardF]

Building on OSX with autotools results in the following:

duplicate symbol _NC_alignments_computed in:
    ../libdispatch/.libs/libdispatch.a(libdispatch_la-doffsets.o)
    ../libdispatch/.libs/libdispatch.a(libdispatch_la-daux.o)
duplicate symbol _NC_alignments_computed in:
    ../libdispatch/.libs/libdispatch.a(libdispatch_la-doffsets.o)
    ../libdap2/.libs/libdap2.a(libdap2_la-daputil.o)
duplicate symbol _NC_alignments_computed in:
    ../libdispatch/.libs/libdispatch.a(libdispatch_la-doffsets.o)
    ../libdap2/.libs/libdap2.a(libdap2_la-ncd2dispatch.o)
duplicate symbol _NC_alignments_computed in:
    ../libdispatch/.libs/libdispatch.a(libdispatch_la-doffsets.o)
    ../libdap4/.libs/libdap4.a(libdap4_la-d4meta.o)
ld: 4 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

This is not observed on other platforms. Working on the fix now.

[DennisHeimbigner]

My speculation is that this is because the declaration in include/ncoffsets.h
int NC_alignments_computed;
is not marked extern (or maybe EXTERNL).

[WardF]

Interesting that the issue only shows up on OSX.