p4est cmake detection

p4est.cmake

# let say we require to use at least p4est version 2.8.5
set(P4EST_MINIMAL_VERSION 2.8.5)

# first try to detect P4ESTConfig.cmake somewhere in the CMAKE_PREFIX_PATH
# if found, we're ready to go using target P4EST::P4EST
find_package(P4EST ${P4EST_MINIMAL_VERSION} CONFIG QUIET)
if(P4EST_FOUND)
  message(STATUS "P4EST was found with find_package, with version ${P4EST_VERSION}")
endif()

# if not found, we may try to detect p4est through pkgconfig (an autotools based build of p4est will provide it)
if(NOT P4EST_FOUND)
  # use pkgconfig
  find_package(PkgConfig REQUIRED)
  pkg_check_modules(PC_P4EST QUIET IMPORTED_TARGET p4est>=${P4EST_MINIMAL_VERSION}) # <=======
  if(PC_P4EST_FOUND)
    message(STATUS "P4EST was found with pkgconfig, with version ${PC_P4EST_VERSION}")
    add_library(P4EST::P4EST ALIAS PkgConfig::PC_P4EST)
  endif()
endif()