[gimp] Coding Style: update regarding tabs in Makefile-s.

[Jehan <jehanp src gnome org>]

commit cfc770b85e3561498e6c2cf6cd1da251b48ab332
Author: Jehan <jehan girinstud io>
Date:   Thu Jan 27 01:19:26 2022 +0100

    Coding Style: update regarding tabs in Makefile-s.
    
    Possibly the only place where we expect them?

 CODING_STYLE.md | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/CODING_STYLE.md b/CODING_STYLE.md
index ced780fd8e..10d4fc756d 100644
--- a/CODING_STYLE.md
+++ b/CODING_STYLE.md
@@ -171,6 +171,10 @@ Even if two spaces for each indentation level allow deeper nesting, GIMP favors
 self-documenting function names that can be quite long. For this reason, you
 should avoid deeply nested code.
 
+*Note*: the only place where we use Tab indentation and alignment is the
+Makefiles. In there, Tab are expected to be displayed as 8 characters
+for proper display
+
 #### Vertical spaces (new lines)
 
 Except for one single newline at the end of the file, other empty lines (at the