Add a selftest run for the TIMING_ALT test

The fuzz programs require one layer of directories
more when adding include directories.
Also remove an unnecessary include directory in the Makefile.

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 127f424..c38f6e4 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -2723,6 +2723,10 @@
 
     msg "test: MBEDTLS_TIMING_ALT - test suites"
     make test TEST_TIMING_ALT_IMPL=1 CFLAGS="-I../tests/src/external_timing"
+
+    msg "selftest - MBEDTLS-TIMING_ALT"
+    make programs TEST_TIMING_ALT_IMPL=1 CFLAGS="-I../../tests/src/external_timing -I../tests/src/external_timing"
+    programs/test/selftest
 }
 
 component_test_platform_calloc_macro () {