[PATCH] srcfiles: fix unused variable BUFFER_SIZE

[Jose Quaresma]

The const variable BUFFER_SIZE is used only on the zip_files
function witch is only available with LIBARCHIVE.

| ../../elfutils-0.191/src/srcfiles.cxx:81:18: error: unused variable 'BUFFER_SIZE' [-Werror,-Wunused-const-variable]
|    81 | constexpr size_t BUFFER_SIZE = 8192;
|       |                  ^~~~~~~~~~~

Signed-off-by: Jose Quaresma <jose.quaresma@foundries.io>
---
 src/srcfiles.cxx | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/srcfiles.cxx b/src/srcfiles.cxx
index 892737cc..09d50f8d 100644
--- a/src/srcfiles.cxx
+++ b/src/srcfiles.cxx
@@ -78,7 +78,9 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = print_version;
 /* Bug report address.  */
 ARGP_PROGRAM_BUG_ADDRESS_DEF = PACKAGE_BUGREPORT;
 
+#ifdef HAVE_LIBARCHIVE
 constexpr size_t BUFFER_SIZE = 8192;
+#endif
 
 /* Definitions of arguments for argp functions.  */
 static const struct argp_option options[] =
-- 
2.44.0