[2.7] Gitignore gmon.out (GH-5796) (GH-6328)

gmon.out is generated when profiling turned on

Full Configuration:
./configure --prefix=$PWD/install --enable-profiling  --enable-big-digits=30
--with-pydebug --with-assertions  --with-valgrind.
(cherry picked from commit 95ad3822)
Co-authored-by: Neeraj Badlani <neerajbadlani@gmail.com>

.gitignore

@@ -86,3 +86,4 @@ TAGS
 coverage/
 externals/
 htmlcov/
+gmon.out