cmake libdwarf examples

nv-legate/legate src/cmake/thirdparty/get_cpptrace.cmake :24 

find_package(libdwarf QUIET)

facebook/folly CMake/folly-deps.cmake :130 

find_package(LibDwarf)

lightspark/lightspark tests/test-runner/3rdparty/cpptrace/CMakeLists.txt :288 

find_package(libdwarf REQUIRED)