[Buildroot] [PATCH 0/4] package/cmake: revert the bump to 3.7

[Jörg Krause]

Hi,

On Sat, 2017-02-25 at 19:51 +0100, Yann E. MORIN wrote:
> Hello All!
> 
> cmake 3.7 causes serious regressions in some cmake-based packages,
> related to how RPATH is handled.

For an explanation what's going wrong please have a look at [1].

> See for example:
> 
>   - domoticz : http://autobuild.buildroot.org/results/fd0/fd0ba54c7ab
> f973691b39a0ca1bb4e07d749593a/
>   - freerdp  : http://autobuild.buildroot.org/results/5d4/5d429d0e288
> 754a541ee5d8be515454c5fccd28b/
>   - libcec   : http://autobuild.buildroot.org/results/3f3/3f3593bab77
> 34dd274faf5b5690895e9424cbb89/
> 
> (and many others)

For example bctoolbox. Although the build errors are fixed, CMake does
not find the optionally mbedTLS package if zlib is available as it
links against the host zlib when using `check_symbol_exists()`.

> All causes the link to be attemped against host libraries, which is
> definitely not appropriate...
> 
> Properly fixing this so close to the release is problematic; we'd
> risk
> having to hunt down packages one by one.

A fix which worked for me was to remove the line `set(CMAKE_SYSTEM_NAME
Linux)` from the toolchainfile to be able to set the flag
`FIND_LIBRARY_USE_LIB32_PATHS` property to `FALSE`. Of course, we also
have to set the necessary flags which are set depending on
`CMAKE_SYSTEM_NAME`. However, reverting CMake is probably much cleaner.

[1] http://lists.busybox.net/pipermail/buildroot/2017-February/183579.h
tml
[2] https://git.buildroot.net/buildroot/tree/support/misc/toolchainfile
.cmake.in#n13