depends: Force CMAKE_EXPORT_NO_PACKAGE_REGISTRY=TRUE #32943

1. 
   hebasto commented at 7:20 pm on July 10, 2025: member

   When using CMake policies 3.14 and below, the export(PACKAGE) command by default populates the user package registry, which is stored outside the build tree. Setting the CMAKE_EXPORT_NO_PACKAGE_REGISTRY variable disables this side effect.

   In CMake 3.15 and later, this behavior is disabled by default, and the variable has no effect.

   This PR forces CMAKE_EXPORT_NO_PACKAGE_REGISTRY=TRUE globally, rather than managing it for each dependency package individually rather. It may be reverted once all CMake-based packages have updated to policies 3.15 or newer.

   Fixes #32938.

2. depends: Force `CMAKE_EXPORT_NO_PACKAGE_REGISTRY=TRUE`

   When using CMake policies 3.14 and below, the `export(PACKAGE)` command
   by default populates the user package registry, which is stored outside
   the build tree. Setting the `CMAKE_EXPORT_NO_PACKAGE_REGISTRY` variable
   disables this side effect.
   
   In CMake 3.15 and later, this behavior is disabled by default, and the
   variable has no effect.

   44f3bae300
3. hebasto added the label Build system on Jul 10, 2025
4. 
   DrahtBot commented at 7:20 pm on July 10, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32943.

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5. 
   theuni commented at 9:54 pm on July 10, 2025: member

   Yikes. Concept ACK.

   • The export(PACKAGE) command does not populate the user package registry when CMP0090 is set to NEW unless the CMAKE_EXPORT_PACKAGE_REGISTRY variable explicitly enables it. When CMP0090 is not set to NEW then export(PACKAGE) populates the user package registry unless the CMAKE_EXPORT_NO_PACKAGE_REGISTRY variable explicitly disables it.
   • CMAKE_FIND_USE_PACKAGE_REGISTRY disables the User Package Registry in all the find_package() calls when set to FALSE.

   Could we also set CMAKE_FIND_USE_PACKAGE_REGISTRY to false in the toolchain file as a belt-and-suspenders in case some future package manually opts-in using CMAKE_EXPORT_PACKAGE_REGISTRY ?

Contributors
hebasto DrahtBot theuni

Labels
Build system