The json.tar.xz rule packed neither src/modules nor tests, but the
top-level CMakeLists.txt needs src/modules for
NLOHMANN_JSON_BUILD_MODULES=ON and defaulted JSON_BuildTests to ON for
a main project. A standalone configure of the extracted archive failed
at add_subdirectory(tests), and enabling the module failed at
add_subdirectory(src/modules).
Add src/modules to the archive, and default JSON_BuildTests to ON only
if tests/CMakeLists.txt exists, so a repository checkout still builds
the tests by default while the archive configures out of the box. Use
GNU tar via a TAR variable (gtar if present, else tar), the same way
SED is found, instead of hard-coding gtar. The library, its public API,
and its ABI are unchanged.
Part of #5716
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann
85fec73da7