[aisleriot] build: Fix build with explicitly specified guile version option

[Christian Persch <chpe src gnome org>]

commit e4e55fd282a23f2093996cc5d906e85b190900e2
Author: Christian Persch <chpe src gnome org>
Date:   Mon May 23 20:44:46 2022 +0200

    build: Fix build with explicitly specified guile version option
    
    Fixes: https://gitlab.gnome.org/GNOME/aisleriot/-/issues/934

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 7bb77bfc..2998c2a3 100644
--- a/meson.build
+++ b/meson.build
@@ -326,7 +326,7 @@ if get_option('guile') == 'auto'
     assert(false, 'Guile not found')
   endif
 else
-  guile_version = get_option('guile').to_string()
+  guile_version = get_option('guile')
 endif
 
 guile_req = 'guile-' + guile_version