FROMLIST: kbuild: lto: fix module versioning

With CONFIG_MODVERSIONS, version information is linked into each
compilation unit that exports symbols. With LTO, we cannot use this
method as all C code is compiled into LLVM bitcode instead. This
change collects symbol versions into .symversions files and merges
them in link-vmlinux.sh where they are all linked into vmlinux.o at
the same time.

Bug: 145210207
Change-Id: Icd8fd0c760891eff7a0ed12ce48b4db2a85fc2ad
Link: https://lore.kernel.org/lkml/20201211184633.3213045-1-samitolvanen@google.com/
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
diff --git a/Makefile b/Makefile
index 58cdffe..439d94c 100644
--- a/Makefile
+++ b/Makefile
@@ -1854,7 +1854,8 @@
 		-o -name '.tmp_*.o.*' \
 		-o -name '*.c.[012]*.*' \
 		-o -name '*.ll' \
-		-o -name '*.gcno' \) -type f -print | xargs rm -f
+		-o -name '*.gcno' \
+		-o -name '*.*.symversions' \) -type f -print | xargs rm -f
 
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