Merge #249: cmake: Fix clang-tidy CI task

dc32026 cmake: Fix `clang-tidy` CI task (Hennadii Stepanov)

Pull request description:

  #192 introduced a regression in the "clang-tidy" CI task. For instance, see https://cirrus-ci.com/task/6601636905222144 from bitcoin#29790.

  The reason is that disabling `EXPORT_COMPILE_COMMANDS` for `secp256k1` target only is not enough because the subtree's build system has other intermediate build targets internally.

ACKs for top commit:
  TheCharlatan:
    ACK dc32026

Tree-SHA512: 134e7106c18abd7f07c15742edd73a16847f09452646ed4408d8cd35f7bca9f8501028f94b718720720c7ecc330a91dfd94680c091d010be88952ce4f4ef4c4e

src/CMakeLists.txt

@@ -67,8 +67,9 @@ foreach(config IN LISTS CMAKE_BUILD_TYPE CMAKE_CONFIGURATION_TYPES)
   string(TOUPPER "${config}" config)
   set(CMAKE_C_FLAGS_${config} "${CMAKE_C_FLAGS_RELWITHDEBINFO}")
 endforeach()
+set(CMAKE_EXPORT_COMPILE_COMMANDS OFF)
 add_subdirectory(secp256k1)
-set_target_properties(secp256k1 PROPERTIES EXPORT_COMPILE_COMMANDS OFF)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 string(APPEND CMAKE_C_COMPILE_OBJECT " ${APPEND_CPPFLAGS} ${APPEND_CFLAGS}")
 
 # Stable, backwards-compatible consensus functionality.