For upstream: -rdynamic is implemented by at least gcc and clang.
Using -export-dynamic with gcc only worked because of what was initially
a gcc implementation quirk.  -rdynamic isn't used at compile time anyway,
so using -rdynamic or -Wl,--export-dynamic in LDFLAGS would be enough.

Index: src/Makefile.in
--- src/Makefile.in.orig
+++ src/Makefile.in
@@ -89,7 +89,7 @@ POST_UNINSTALL = :
 build_triplet = @build@
 host_triplet = @host@
 bin_PROGRAMS = klavaro$(EXEEXT)
-@IS_POSIX_TRUE@am__append_1 = -export-dynamic
+@IS_POSIX_TRUE@am__append_1 =
 @IS_WIN_TRUE@am__append_2 = -mwindows
 subdir = src
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
