[gtk+] Add ignore file for macro dir

[Emmanuele Bassi <ebassi src gnome org>]

commit 9e1afd7ba8dfc0edade1f8af7bd0635067589133
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Wed Aug 3 11:49:15 2016 +0100

    Add ignore file for macro dir
    
    The contents of the macro directory are too complicated for git.mk to
    handle: the contents are filled by autotools and may change between
    systems or autotools releases; and we additionally ship our own m4
    macros.
    
    To avoid unnecessary noise on the `git status` output we should simply
    add an ignore file specifically for the macro directory.

 m4/.gitignore |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/m4/.gitignore b/m4/.gitignore
new file mode 100644
index 0000000..d425a91
--- /dev/null
+++ b/m4/.gitignore
@@ -0,0 +1,3 @@
+!/ax_prog_cc_for_build.m4
+!/pkg_config_for_build.m4
+*.m4