Documentation: kbuild: note CONFIG_DEBUG_EFI in reproducible builds

CONFIG_EFI_DEBUG embeds absolute file paths into object files, which
makes the resulting vmlinux specific to the build environment.

Add a note about this in reproducible-builds.rst

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nicolas Schier <nsc@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20250924-kbuild-doc-config-debug-efi-in-reproducible-builds-v2-1-d2d6b9dcdb7d@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Author: masahir0y

Documentation/kbuild/reproducible-builds.rst

@@ -61,6 +61,9 @@ supported.
 The Reproducible Builds web site has more information about these
 `prefix-map options`_.
 
+Some CONFIG options such as `CONFIG_DEBUG_EFI` embed absolute paths in
+object files. Such options should be disabled.
+
 Generated files in source packages
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