Rec: Don't fail configure on missing fcontext.hpp

Fixes #4014

diff --git a/pdns/recursordist/configure.ac b/pdns/recursordist/configure.ac
index 5fcf6a2c947595b526b5fb06026fed2a0d7ec956..0ee0c5a17e607c1737840ca9c1c0564021196549 100644 (file)
--- a/pdns/recursordist/configure.ac
+++ b/pdns/recursordist/configure.ac
@@ -54,7 +54,9 @@ AC_DEFUN([PDNS_SELECT_CONTEXT_IMPL], [
       LDFLAGS="$LDFLAGS $BOOST_THREAD_LDFLAGS"
     fi
     AC_MSG_NOTICE([checking whether the Boost context library actually links...])
-    BOOST_FIND_LIB([context], [$1], [boost/context/fcontext.hpp], [[]])
+    BOOST_FIND_HEADER([boost/context/fcontext.hpp], [ : ], [
+      BOOST_FIND_LIB([context], [$1], [boost/context/fcontext.hpp], [[]])
+    ])
     case $boost_cv_lib_context in
       (yes)
         AC_MSG_NOTICE([MTasker will use the Boost context library for context switching])