Add extra `-shared` to link.so command.

While compiling OpenADK I discovered that
there may be a case where UCLIBC_EXTRA_LDFLAGS
contains `-fpie -pie`. Linker ignores `-shared`
if `-pie` flag is passed after and produces
an executable binary instead of shared object.
This leads to linking failure because `ld-uClibc.so.1`
becomes executable instead of shared object.
`ld-uClibc.so.1` is used as one of the inputs
when linking of libc.so.1 and linking proccess fails.
To prevent this issue we need to pass extra `-shared` flag
in `link.so` target command after all other flags to overwrite
`-pie` effect.

Signed-off-by: Dmitry Chestnykh <dm.chestnykh@gmail.com>

Makerules

@@ -334,7 +334,7 @@ define link.so
 		-Wl,-soname=$(notdir $@).$(2) \
 		$(CFLAG_-nostdlib) $(CFLAG_-nostartfiles) \
 		-o $(dir $@)$(1) $(START_FILE-$(notdir $@)) \
-		-Wl,--whole-archive $(firstword $^) -Wl,--no-whole-archive \
+		-Wl,--whole-archive $(firstword $^) -Wl,--no-whole-archive -shared \
 		$(LIBS-$(notdir $@)) $(LIBGCC) $(END_FILE-$(notdir $@))
 	$(Q)$(LN) -sf $(1) $@.$(2)
 	$(Q)$(LN) -sf $(1) $@