git: don't ignore fuzz/Makefile

*/Makefile is ignored (because it's created by cmake in in-tree builds).
But fuzz/Makefile is checked into git, so don't ignore it.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/programs/.gitignore b/programs/.gitignore
index 6c8c515..33593e0 100644
--- a/programs/.gitignore
+++ b/programs/.gitignore
@@ -1,4 +1,7 @@
+# Ignore makefiles generated by CMake, but not the makefile that's checked in.
 */Makefile
+!fuzz/Makefile
+
 *.sln
 *.vcxproj