clang-12: No CMAKE_CXX_COMPILER could be found.

[strk]

I get No CMAKE_CXX_COMPILER could be found. from cmake even if I installed clang-12 package, which according to apt provides the c++-compiler virtual package on Ubuntu-20.04

[strk]

NOTE: installing g++ fixes the build

[lnicola]

Just like autoconf, CMake respects CC and CXX, so you can run CC=clang CXX=clang++ cmake ... But this seems like an alternatives issue. GEOS isn't supposed to work around distribution choices.