LAPACK master does not compile with CMake 3.9

[christoph-conrads]

Description

The latest LAPACK code in commit fe843f99d6ad0034cdc85cd3d56f164b923afbe9 fails to compile with CMake 3.10 because object files are linked against a library. This features was only added in CMake 3.12 (cf. CMake: target_link_libraries -- Linking Object Libraries).

Example:

$ cmake ~/lapack
[snip]
CMake Error at SRC/CMakeLists.txt:530 (target_link_libraries):
  Object library target "lapack_obj" may not link to anything.

-- Configuring incomplete, errors occurred!
See also "/tmp/tmp.CRCZ8x92Ba/CMakeFiles/CMakeOutput.log".
See also "/tmp/tmp.CRCZ8x92Ba/CMakeFiles/CMakeError.log".
$ cmake --version
cmake version 3.10.2

CMake suite maintained and supported by Kitware (kitware.com/cmake).

Other problems breaking CMake 3.9 compatibility:

• The use of the Fortran_PREPROCESS property added in CMake 3.15

Possible fixes:

• Bump the minimum CMake version to ~3.12~ 3.15
• Do not link object file libraries

Checklist

• [x] I've included a minimal example to reproduce the issue
• [ ] I'd be willing to make a PR to solve this issue