Add suffix to Half library name

[bryab]

This was necessary for me to build on macOS.

[cessen]

Hmm... that's odd. I wonder if the Ilm libraries build with different names on MacOS? On Linux on my machine, the library files are named like so (building them from source):

libHalf.a      libIexMath-2_2.a     libIlmThread-2_2.a
libHalf.la     libIexMath-2_2.la    libIlmThread-2_2.la
libIex-2_2.a   libIlmImf-2_2.a      libImath-2_2.a
libIex-2_2.la  libIlmImfUtil-2_2.a  libImath-2_2.la

The libHalf library files don't have the -2_2 suffix. So I think this PR would break things on Linux...? Can you double-check what your library files are named?

[bryab]

Hey, I think this is an issue with version 2.3. Just tried building on Linux, and I got:

openexr2.3/lib/libIex-2_3_s.a
openexr2.3/lib/libIlmImf-2_3_s.a
openexr2.3/lib/libIexMath-2_3_s.a
openexr2.3/lib/libHalf-2_3_s.a
openexr2.3/lib/libIlmImfUtil-2_3_s.a
openexr2.3/lib/libImath-2_3_s.a
openexr2.3/lib/libIlmThread-2_3_s.a

[norru]

My guess: there should be an option in the build to remove the suffix which is now the default but wasn't in previous versions. Could be unintentional from the lib's maintainer. I think the version suffix shouldn't be used.