librt: Use -nodefaultlibs instead of -nostdlib

nostdlib disables linking in startup files too which is not
what we want here since it needs to resolve __dso_handle
which comes from crtbeginS.o, otherwise librt has this
undefined reference to a weak undefined __dso_handle that
shows up as error (with gold linker)
when shared libraries are being built which are
linking in librt

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

librt/Makefile.in

@@ -15,6 +15,9 @@ LIBS-librt.so := $(LIBS)
 ifeq ($(UCLIBC_HAS_THREADS_NATIVE),y)
 LIBS-librt.so += $(top_builddir)lib/libdl.so $(top_builddir)lib/libpthread.so
 endif
+START_FILE-librt.so := $(SHARED_START_FILES)
+END_FILE-librt.so := $(SHARED_END_FILES)
+
 
 librt_FULL_NAME := librt-$(VERSION).so