tz's makefile can only build in-tree. It *installs* to a different directory (specified by `DESTDIR`), but the build artifacts are left in the source tree, including `zic.o`, `zic`, etc. This is disruptive to CMake builds which are usually out-of-tree. To work around this, copy the whole source tree to a path under `CMAKE_CURRENT_BINARY_DIR`, and build it from there. It's a tiny project so the cost of copying is not significant.
tz
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