[libgit2-glib] meson: Fix `b_ndebug` workaround

[Iñigo Martínez <inigomartinez src gnome org>]

commit c85e258c83c426252beb5f4ac223aca562470de0
Author: Iñigo Martínez <inigomartinez gmail com>
Date:   Mon Nov 12 12:29:09 2018 +0100

    meson: Fix `b_ndebug` workaround
    
    There is a workaround present in the source root meson build file
    due to a bug in an older meson version[0]. The workaround is wrong
    and is fixed now.
    
    [0] https://github.com/mesonbuild/meson/pull/1896

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 13ddcdd..1965d14 100644
--- a/meson.build
+++ b/meson.build
@@ -96,7 +96,7 @@ endif
 
 # Workaround for meson's bug
 # https://github.com/mesonbuild/meson/pull/1896
-if get_option('b_ndebug') == true
+if get_option('b_ndebug') == 'true'
   common_flags += ['-DG_DISABLE_ASSERT']
 endif