[eog] build: it's enable_xmp not enable_exempi

[Felix Riemann <friemann src gnome org>]

commit 75612239755c278244934eccdfc96a2b41224886
Author: Rasmus Thomsen <cogitri exherbo org>
Date:   Thu May 10 12:13:17 2018 +0200

    build: it's enable_xmp not enable_exempi

 src/meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/meson.build b/src/meson.build
index 1c02b23..747b76b 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -88,7 +88,7 @@ if enable_libexif
   sources += files('eog-exif-util.c')
 endif
 
-if enable_libexif or enable_exempi
+if enable_libexif or enable_xmp
   sources += files('eog-metadata-details.c')
 endif