[libsoup] Meson: Add fallback for libpsl

[Tomas Popela <tpopela src gnome org>]

commit f462a18f05978c7a83f62a64ccc85d1616ddf297
Author: Xavier Claessens <xavier claessens collabora com>
Date:   Fri Dec 7 10:45:00 2018 -0500

    Meson: Add fallback for libpsl
    
    libpsl has a Meson build system upstream now, we can use it to build
    libpsl as subproject.

 meson.build | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index c8347e1f..f3337dc0 100644
--- a/meson.build
+++ b/meson.build
@@ -101,7 +101,8 @@ if not is_static_library
 endif
 
 libpsl_required_version = '>= 0.20'
-libpsl_dep = dependency('libpsl', version : libpsl_required_version)
+libpsl_dep = dependency('libpsl', version : libpsl_required_version,
+  fallback : ['libpsl', 'libpsl_dep'])
 
 if cc.has_function('gmtime_r', prefix : '#include <time.h>', args : default_source_flag)
     cdata.set('HAVE_GMTIME_R', '1')