avoid __memcat_p link failure

The kernel test robot reports a link error when the stm driver is a
loadable module on any v5.4 kernel:

> ERROR: "__memcat_p" [drivers/hwtracing/stm/stm_core.ko] undefined!

This was fixed in mainline with commit 7273ad2b08 ("kbuild: link
lib-y objects to vmlinux forcibly when CONFIG_MODULES=y"), which
is fairly intrusive.

Fix the v5.4 specific issue with a minimal subset of that patch,
linking only the failing object into the kernel. Kernels before v4.20
are not affected.

Reported-by: kernel test robot <lkp@intel.com>
Link: https://groups.google.com/g/clang-built-linux/c/H-PrABqYShg
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

lib/Makefile

@@ -31,7 +31,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 flex_proportions.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
 	 earlycpio.o seq_buf.o siphash.o dec_and_lock.o \
-	 nmi_backtrace.o nodemask.o win_minmax.o memcat_p.o
+	 nmi_backtrace.o nodemask.o win_minmax.o
 
 lib-$(CONFIG_PRINTK) += dump_stack.o
 lib-$(CONFIG_MMU) += ioremap.o
@@ -46,7 +46,7 @@ obj-y += bcd.o sort.o parser.o debug_locks.o random32.o \
 	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \
 	 percpu-refcount.o rhashtable.o \
 	 once.o refcount.o usercopy.o errseq.o bucket_locks.o \
-	 generic-radix-tree.o
+	 generic-radix-tree.o memcat_p.o
 obj-$(CONFIG_STRING_SELFTEST) += test_string.o
 obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o