Add changelog entry

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/ChangeLog.d/build-without-certs.txt b/ChangeLog.d/build-without-certs.txt
new file mode 100644
index 0000000..9bb7384
--- /dev/null
+++ b/ChangeLog.d/build-without-certs.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix the build of sample programs when MBEDTLS_PEM_C is enabled but
+     MBEDTLS_CERTS_C is disabled. Reported by Michael Schuster in #4206.