[gnome-system-monitor] Fixes #78: Fix translations after porting to meson

[Robert Roth <robertroth src gnome org>]

commit e093fab4785dbd0cd4d9ef36d0a8f08596e4b8ca
Author: Ting Wei Lan <lantw src gnome org>
Date:   Sat Jun 2 21:48:52 2018 +0300

    Fixes #78: Fix translations after porting to meson
    
    Most dir options in meson are relative to prefix. When we want absolute
    paths, we have to join them with prefix ourselves.

 meson.build | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/meson.build b/meson.build
index 4bdf6da7..08e71283 100644
--- a/meson.build
+++ b/meson.build
@@ -21,10 +21,10 @@ conf = configuration_data()
 conf.set_quoted('VERSION', meson.project_version())
 conf.set_quoted('GETTEXT_PACKAGE', gettext_package)
 conf.set_quoted('GNOMELOCALEDIR',
-  join_paths(get_option('datadir'), 'locale')
+  join_paths(get_option('prefix'), get_option('localedir'))
 )
 conf.set_quoted('GSM_LIBEXEC_DIR',
-  join_paths(get_option('libexecdir'), meson.project_name())
+  join_paths(get_option('prefix'), get_option('libexecdir'), meson.project_name())
 )
 
 dataconf = configuration_data()