https://github.com/airspy/airspyhf/pull/35
https://build.opensuse.org/package/view_file/openSUSE:Factory/airspyhf/airspyhf-fix-libm-linking.patch

diff --git a/libairspyhf/src/CMakeLists.txt b/libairspyhf/src/CMakeLists.txt
index 9d8d483..da1f966 100644
--- a/libairspyhf/src/CMakeLists.txt
+++ b/libairspyhf/src/CMakeLists.txt
@@ -58,7 +58,7 @@ set_target_properties(airspyhf PROPERTIES CLEAN_DIRECT_OUTPUT 1)
 set_target_properties(airspyhf-static PROPERTIES CLEAN_DIRECT_OUTPUT 1)
 
 # Dependencies
-target_link_libraries(airspyhf ${LIBUSB_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries(airspyhf ${LIBUSB_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT} m)
 
 # For cygwin just force UNIX OFF and WIN32 ON
 if( ${CYGWIN} )

diff --git a/libairspyhf/libairspyhf.pc.in b/libairspyhf/libairspyhf.pc.in
index fcf040b..ca5214f 100644
--- a/libairspyhf/libairspyhf.pc.in
+++ b/libairspyhf/libairspyhf.pc.in
@@ -7,5 +7,5 @@ Name: AirSpy HF+ Library
 Description: C Utility Library
 Version: @VERSION@
 Cflags: -I${includedir}/libairspyhf/ @AIRSPYHF_PC_CFLAGS@
-Libs: -L${libdir} -lairspyhf
+Libs: -L${libdir} -lairspyhf -lm
 Libs.private: @AIRSPYHF_PC_LIBS@
