comms/gnuradio: unbreak with boost 1.67

gr-blocks/lib/message_strobe_impl.cc:93:35: error: no matching conversion for functional-style cast from 'float' to 'boost::posix_time::milliseconds' (aka 'subsecond_duration<boost::posix_time::time_duration, 1000>')

boost::this_thread::sleep(boost::posix_time::milliseconds(d_period_ms));
                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

/usr/local/include/boost/date_time/time_duration.hpp:270:30: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'float' to 'const boost::date_time::subsecond_duration<boost::posix_time::time_duration, 1000>' for 1st argument

class BOOST_SYMBOL_VISIBLE subsecond_duration : public base_duration
                           ^

/usr/local/include/boost/date_time/time_duration.hpp:286:59: note: candidate template ignored: disabled by 'enable_if' [with T = float]

typename boost::enable_if<boost::is_integral<T>, void>::type* = 0) :
                          ^

/usr/local/bin/ld: CMakeFiles/tags_demo.dir/tags_demo.cc.o: undefined reference to symbol 'pthread_condattr_init@@FBSD_1.0'
//lib/libthr.so.3: error adding symbols: DSO missing from command line
c++: error: linker command failed with exit code 1 (use -v to see invocation)

• [gr-uhd/examples/c++/tags_demo] Error code 1

PR: 227427
Reported by: antoine (via exp-run)
Obtained from: Homebrew