While GNU tar automatically detects the used compression algorithm,
POSIX requires that we specify -z if the tarball is compressed with
gzip.
Fixes a build error on OpenBSD.
We have seen some cases where the build fails for folks, and they are
missing unzip/tar/gzip etc. We can catch some of these in CMake itself,
so lets make sure to handle that uniformly across the build system.
The REQUIRED flag to `find_program` was only added on in CMake 3.18 and
above, so we can't rely on that to actually halt the program execution.
The IANA Time Zone Database contains data needed, at least, for various
JavaScript objects. This adds plumbing for a parser and code generator
for this data. The generated data will be made available by LibTimeZone,
much like how UCD and CLDR data is available through LibUnicode.
