libc: Symlink libm.a to libc.a

Some programs (or g++) might want to link against libm, yet on Luna it's part of libc.

libs/libc/Makefile

@@ -59,6 +59,8 @@ build: $(LIBC_BIN)/crt0.o $(LIBC_BIN)/crti.o $(LIBC_BIN)/crtn.o $(LIBC_BIN)/libc
 $(DESTDIR)/libc.a: $(LIBC_BIN)/libc.a
 	@mkdir -p $(@D)
 	@cp $^ $@
+	@rm -f $(DESTDIR)/libm.a
+	@ln -s $@ $(DESTDIR)/libm.a
 	@echo "  INSTALL $^"
 
 $(DESTDIR)/crt0.o: $(LIBC_BIN)/crt0.o