[PATCH gpgmepy] dist: Improve header search

With this change, `/usr/include` will be searched for the required
headers. Before this change, this was dead code as include_dirs is
always set.
---
 setup.py.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/setup.py.in b/setup.py.in
index 4cf8835..309bf42 100755
--- a/setup.py.in
+++ b/setup.py.in
@@ -106,7 +106,7 @@ if not gpgme_h:
     if os.path.exists(os.path.join('@prefix@', 'include', 'gpgme.h')):
         gpgme_h = os.path.join('@prefix@', 'include', 'gpgme.h')
     else:
-        for include_dir in (include_dirs or ['/usr/include']):
+        for include_dir in (include_dirs + ['/usr/include']):
             if os.path.exists(os.path.join(include_dir, 'gpgme.h')):
                 gpgme_h = os.path.join(include_dir, 'gpgme.h')
                 break
-- 
2.49.0