check for ld support of -Bsymbolic-functions; disable shared if not avail

this issue affects the last gpl2 version of binutils, which some
people are still using out of aversion to gpl3. musl requires
-Bsymbolic-functions because it's the only way to make a libc.so
that's able to operate prior to dynamic linking but that still behaves
correctly with respect to global vars that may be moved to the main
program via copy relocations.

configure

@@ -267,6 +267,13 @@ fi
 tryflag CFLAGS_AUTO -fno-stack-protector
 tryldflag LDFLAGS_AUTO -Wl,--hash-style=sysv
 
+# Disable dynamic linking if ld is broken and can't do -Bsymbolic-functions
+LDFLAGS_DUMMY=
+tryldflag LDFLAGS_DUMMY -Wl,-Bsymbolic-functions || {
+printf "warning: disabling dynamic linking support\n"
+shared=no
+}
+
 
 printf "creating config.mak... "