[babl] Fix : libdir for autotools and meson are not the same…

[Félix Piédallu <fpiedallu src gnome org>]

commit e9b81a1c6c290608a2c9107a2af8930af45c295d
Author: Félix Piédallu <felix piedallu me>
Date:   Mon Dec 18 15:06:57 2017 +0100

    Fix : libdir for autotools and meson are not the same…

 babl/meson.build |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/babl/meson.build b/babl/meson.build
index a46a7f5..b3058cc 100644
--- a/babl/meson.build
+++ b/babl/meson.build
@@ -81,8 +81,8 @@ install_headers(babl_headers,
 babl = library(lib_name,
   babl_sources,
   include_directories: [ rootInclude, bablBaseInclude],
-  c_args:   [ '-DLIBDIR="' + get_option('libdir') + '"', ],
-  cpp_args: [ '-DLIBDIR="' + get_option('libdir') + '"', ],
+  c_args:   [ '-DLIBDIR="' + join_paths(get_option('prefix'), get_option('libdir')) + '"', ],
+  cpp_args: [ '-DLIBDIR="' + join_paths(get_option('prefix'), get_option('libdir')) + '"', ],
   link_with: [ babl_base, ],
   link_args: [ '-Wl,--version-script,' + version_script, ],
   dependencies: [ math, thread, dl, ],