Follow-up to 4e04ec8, which caused a regression on OS X.
Checking the value of CMAKE_THREAD_LIBS_INIT to decide whether any threading
library is present on a system turns out to be wrong -- in OS X, for
example, usage of pthreads does not depend on any additional linker or
compiler flags, so CMAKE_THREAD_LIBS_INIT is empty and our check in
src/CMakeLists.txt failed (it used to work before 4e04ec8 because
CMAKE_HAVE_THREADS_LIBRARY is set).
Instead, just look for Threads_FOUND, which FindThreads sets just like any
other Find module when it has found what it was looking for.
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
As mentioned in the previous commit, there are cases where
CMAKE_HAVE_THREADS_LIBRARY is not set and pthreads _is_ being used: one can
pass -DTHREADS_HAVE_PTHREAD_ARG=1 to CMake directly so that it just passes
-pthread to the compiler/linker and does not set CMAKE_HAVE_THREADS_LIBRARY.
Since we are only interested in knowing whether any threading library has
been found, we should use CMAKE_THREAD_LIBS_INIT instead (Threads_FOUND
would also work).
Note that, at the moment, there is only a pthreads backend available in
threads/, so if it is not found configuration will fail because CMake will
try to create a library from an empty set of source files.
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
