armel/mipsel/powerpc/riscv64 need -latomic

https://buildd.debian.org/status/logs.php?pkg=pgagroal&ver=1.5.0-1

--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -32,6 +32,7 @@ if (${CMAKE_SYSTEM_NAME} STREQUAL "Linux
     ${OPENSSL_CRYPTO_LIBRARY}
     ${OPENSSL_SSL_LIBRARY}
     ${SYSTEMD_LIBRARIES}
+    atomic
   )
 
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--no-undefined")
