[cpm] Bump to 0.32.1, fixes BUILD_SHARED_LIBS=ON having no effect.

cpm 0.32 introduces a scope encapsulation:

https://github.com/cpm-cmake/CPM.cmake/releases/tag/v0.32.0

scripts/cmake/CPM.cmake

-set(CPM_DOWNLOAD_VERSION 0.31.1)
+set(CPM_DOWNLOAD_VERSION 0.32.1)
 
 if(CPM_SOURCE_CACHE)
   # Expand relative path. This is important if the provided path contains a tilde (~)