Only in a/host: build
diff -aur a/host/lib/usrp/cores/rx_dsp_core_3000.cpp b/host/lib/usrp/cores/rx_dsp_core_3000.cpp
--- a/host/lib/usrp/cores/rx_dsp_core_3000.cpp	2021-06-12 07:17:40.663375708 +0200
+++ b/host/lib/usrp/cores/rx_dsp_core_3000.cpp	2021-06-12 07:06:01.870025559 +0200
@@ -15,6 +15,7 @@
 #include <boost/assign/list_of.hpp>
 #include <boost/bind.hpp>
 #include <boost/math/special_functions/round.hpp>
+#include <boost/math/special_functions/sign.hpp>
 #include <boost/thread/thread.hpp> //thread sleep
 #include <algorithm>
 #include <cmath>
diff -aur a/host/lib/usrp/cores/rx_frontend_core_3000.cpp b/host/lib/usrp/cores/rx_frontend_core_3000.cpp
--- a/host/lib/usrp/cores/rx_frontend_core_3000.cpp	2020-01-01 05:21:49.000000000 +0100
+++ b/host/lib/usrp/cores/rx_frontend_core_3000.cpp	2021-06-12 07:04:52.246690548 +0200
@@ -13,6 +13,7 @@
 #include <boost/assign/list_of.hpp>
 #include <boost/bind.hpp>
 #include <boost/math/special_functions/round.hpp>
+#include <boost/math/special_functions/sign.hpp>
 
 using namespace uhd;
 
diff -aur a/host/lib/usrp/usrp2/usrp2_impl.cpp b/host/lib/usrp/usrp2/usrp2_impl.cpp
--- a/host/lib/usrp/usrp2/usrp2_impl.cpp	2020-01-01 05:21:49.000000000 +0100
+++ b/host/lib/usrp/usrp2/usrp2_impl.cpp	2021-06-11 21:09:09.120100971 +0200
@@ -835,6 +835,9 @@
     }
 }
 
+#include <boost/math/special_functions/round.hpp>
+#include <boost/math/special_functions/sign.hpp>
+
 double usrp2_impl::set_tx_dsp_freq(
     const std::string &mb,
     const double freq_
@@ -878,9 +881,6 @@
     );
 }
 
-#include <boost/math/special_functions/round.hpp>
-#include <boost/math/special_functions/sign.hpp>
-
 void usrp2_impl::update_clock_source(const std::string &mb, const std::string &source){
     //NOTICE: U2_REG_MISC_CTRL_CLOCK is on the wb clock, and cannot be set from fifo_ctrl
     //clock source ref 10mhz