[gtk-doc] Add build/ dir as convenience when building the module with meson

[Sébastien Wilmet <swilmet src gnome org>]

commit 3de9b63208dd089bb977d930ee9861ec6decc77e
Author: Sébastien Wilmet <swilmet informatique-libre be>
Date:   Fri May 6 23:11:44 2022 +0200

    Add build/ dir as convenience when building the module with meson
    
    Meson requires builddir != srcdir, so always having an empty build/ dir
    is convenient.

 build/.gitignore | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/build/.gitignore b/build/.gitignore
new file mode 100644
index 0000000..72e8ffc
--- /dev/null
+++ b/build/.gitignore
@@ -0,0 +1 @@
+*