[PATCH RFC 03/11] printversion: Fix unused variable

[Ilya Leoshkevich <iii@linux.ibm.com>]

clang complains:

    debuginfod.cxx:354:1: error: unused variable 'apba__' [-Werror,-Wunused-const-variable]
    ARGP_PROGRAM_BUG_ADDRESS_DEF = PACKAGE_BUGREPORT;
    ^
    ../lib/printversion.h:47:21: note: expanded from macro 'ARGP_PROGRAM_BUG_ADDRESS_DEF'
      const char *const apba__ __asm ("argp_program_bug_address")
                        ^

This is as expected: it's used by argp via the
"argp_program_bug_address" name, which is not visible on the C level.
Add __attribute__ ((used)) to make sure that the compiler emits it.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 lib/printversion.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/printversion.h b/lib/printversion.h
index a9e059ff..d1c3a987 100644
--- a/lib/printversion.h
+++ b/lib/printversion.h
@@ -44,6 +44,7 @@ void print_version (FILE *stream, struct argp_state *state);
   void (*const apvh) (FILE *, struct argp_state *) \
    __asm ("argp_program_version_hook")
 #define ARGP_PROGRAM_BUG_ADDRESS_DEF \
-  const char *const apba__ __asm ("argp_program_bug_address")
+  const char *const apba__ __asm ("argp_program_bug_address") \
+  __attribute__ ((used))
 
 #endif // PRINTVERSION_H
-- 
2.39.1