Add changelog entry

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/ChangeLog.d/iar-gcc-perf.txt b/ChangeLog.d/iar-gcc-perf.txt
new file mode 100644
index 0000000..fb0fbb1
--- /dev/null
+++ b/ChangeLog.d/iar-gcc-perf.txt
@@ -0,0 +1,2 @@
+Features
+   * Improve performance for gcc (versions older than 9.3.0) and IAR.