Generate build time and date message at link time.

So it updates each time a bootloader changes, not just when bl*_main.c
files are recompiled.

Fixes ARM-software/tf-issues#33

Change-Id: Ie8e1a7bd7e1913d2e96ac268606284f76af8c5ab
Signed-off-by: Jon Medhurst <tixy@linaro.org>
diff --git a/bl1/bl1_main.c b/bl1/bl1_main.c
index b3adc25..401a525 100644
--- a/bl1/bl1_main.c
+++ b/bl1/bl1_main.c
@@ -70,7 +70,7 @@
 
 	/* Announce our arrival */
 	printf(FIRMWARE_WELCOME_STR);
-	printf("Built : %s, %s\n\r", __TIME__, __DATE__);
+	printf("%s\n\r", build_message);
 
 	/*
 	 * Find out how much free trusted ram remains after BL1 load