fix mklibs with musl

crate a relative symlink to libc.so because
make wildcard function ignores broken symlinks

SVN-Revision: 46123

toolchain/musl/patches/300-relative.patch

@@ -0,0 +1,11 @@
+--- a/Makefile
++++ b/Makefile
+@@ -180,7 +180,7 @@ $(DESTDIR)$(includedir)/%: include/%
+ 	$(INSTALL) -D -m 644 $< $@
+ 
+ $(DESTDIR)$(LDSO_PATHNAME): $(DESTDIR)$(libdir)/libc.so
+-	$(INSTALL) -D -l $(libdir)/libc.so $@ || true
++	$(INSTALL) -D -l libc.so $@ || true
+ 
+ install-libs: $(ALL_LIBS:lib/%=$(DESTDIR)$(libdir)/%) $(if $(SHARED_LIBS),$(DESTDIR)$(LDSO_PATHNAME),)
+