cmake find_library() vs depends

[Jonathan Perkin <jperkin%mnx.io@localhost>]

CMake's find_library() function is apparently not fit for purpose in a 
pkgsrc environment.  It is not buildlink-aware, and will simply go 
looking around the file system for arbitrary libraries.

This causes a problem with e.g. execinfo:

  https://us-central.manta.mnx.io/pkgsrc/public/reports/Darwin/12.3/x86_64/20240510.1437/protobuf-c-1.5.0nb4/build.log

as cmake depends on a bunch of packages, which are pulled into the file 
system for any package that uses cmake as a build-time dependency.

It looks like there are a number of hacks trying to work around this, 
for example:

  $ git grep -C2 rm:-lexecinfo
  devel/abseil/Makefile-.if ${OPSYS} == "Darwin"
  devel/abseil/Makefile-.  if exists(${OSX_SDK_PATH}/usr/include/execinfo.h)
  devel/abseil/Makefile:BUILDLINK_TRANSFORM+=     rm:-lexecinfo
  devel/abseil/Makefile-.  endif
  devel/abseil/Makefile-.endif
  --
  x11/qt5-qtbase/Makefile-# -lexecinfo is bundled in libc
  x11/qt5-qtbase/Makefile-.  if exists(${OSX_SDK_PATH}/usr/include/execinfo.h)
  x11/qt5-qtbase/Makefile:BUILDLINK_TRANSFORM+=           rm:-lexecinfo
  x11/qt5-qtbase/Makefile-.  endif
  x11/qt5-qtbase/Makefile-.elif ${OPSYS} == "Linux"
  --
  x11/qt6-qtbase/Makefile-# -lexecinfo is bundled in libc
  x11/qt6-qtbase/Makefile-.  if exists(${OSX_SDK_PATH}/usr/include/execinfo.h)
  x11/qt6-qtbase/Makefile:BUILDLINK_TRANSFORM+=           rm:-lexecinfo
  x11/qt6-qtbase/Makefile-.  endif
  x11/qt6-qtbase/Makefile-.elif ${OPSYS} == "Linux"

and no doubt this is biting us in other places for the other 
dependencies that cmake pulls in.

In the specific case of libexecinfo, why does cmake depend on it?  I've 
built it fine without the include on both macOS and SmartOS.  Given this 
problem, I'd prefer it if cmake was built with as few dependencies as 
possible.

I'd go further and argue we should have two cmake packages.  One that is 
as small as possible that is only used for building packages (let's call 
it cmake-build or something), and then the main cmake package that is 
full-featured with e.g. curl support (that we would never want enabled 
for building anyway) for end users to use outside of pkgsrc.

--
Jonathan Perkin   -   mnx.io   -   pkgsrc.smartos.org
Open Source Complete Cloud   www.tritondatacenter.com