FTBFS with ECM version >= 5.80.0.

[karuboniru]

Error message

../src/lib/configlib/iso639.cpp: In constructor 'fcitx::kcm::Iso639::Iso639()':
../src/lib/configlib/iso639.cpp:55:41: error: 'ISOCODES_ISO639_2_JSON' was not declared in this scope
   55 |     iso639_2data_ = readAlpha3ToNameMap(ISOCODES_ISO639_2_JSON, "639-2");
      |                                         ^~~~~~~~~~~~~~~~~~~~~~
../src/lib/configlib/iso639.cpp:56:41: error: 'ISOCODES_ISO639_3_JSON' was not declared in this scope
   56 |     iso639_3data_ = readAlpha3ToNameMap(ISOCODES_ISO639_3_JSON, "639-3");
      |                                         ^~~~~~~~~~~~~~~~~~~~~~
../src/lib/configlib/iso639.cpp:57:41: error: 'ISOCODES_ISO639_5_JSON' was not declared in this scope
   57 |     iso639_5data_ = readAlpha3ToNameMap(ISOCODES_ISO639_5_JSON, "639-5");
      |                                         ^~~~~~~~~~~~~~~~~~~~~~

with a config.h with those lines:

/* #undef ISOCODES_ISO639_2_JSON */
/* #undef ISOCODES_ISO639_3_JSON */
/* #undef ISOCODES_ISO639_5_JSON */

---

This should be due to ECM version >= 5.80.0 ships /usr/share/ECM/find-modules/FindIsoCodes.cmake that overrides your cmake/FindIsoCodes.cmake.