Boost has dropped the system library from recent releases, specifically 1.90.0, header files are sufficient now, but as a result gr-iqbal will no longer build. I see gr-iqbal hasn't had any love for a long time now so this probably won't get fixed any time soon. Gentoo users can work around this meanwhile with the following patch to gr-iqbal :-
diff --git a/CMakeLists.txt b/CMakeLists.txt
index bde2b8d..aa670ff 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -71,7 +71,8 @@ endif()
########################################################################
# Find boost
########################################################################
-find_package(Boost "1.65" REQUIRED system)
+#find_package(Boost "1.65" REQUIRED system)
+find_package(Boost "1.65" REQUIRED)
if(NOT Boost_FOUND)
message(FATAL_ERROR "Boost required to compile iqbalance")
... Just paste that into a file and drop it in
/etc/portage/patches/net-wireless/gr-iqbal-0.38.3 and all will be well.