build: remove `MAKE_BUILD_STRINGS` function

This function causes the build message to be generated and compiled in
two different ways, with one way done inside `build_macros.mk` and the
other done inside `windows.mk`, mostly because it's done by generating
the C file on the command line.

We can instead replace this whole build message generation sequence with
a simple standard C compilation command and a normal C file.

Change-Id: I8bc136380c9585ddeec9a11154ee39ef70526f81
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/bl1/bl1_main.c b/bl1/bl1_main.c
index 1dfdc45..9f19b4a 100644
--- a/bl1/bl1_main.c
+++ b/bl1/bl1_main.c
@@ -13,6 +13,7 @@
 #include <arch_helpers.h>
 #include <bl1/bl1.h>
 #include <common/bl_common.h>
+#include <common/build_message.h>
 #include <common/debug.h>
 #include <drivers/auth/auth_mod.h>
 #include <drivers/auth/crypto_mod.h>
@@ -73,7 +74,7 @@
 
 	/* Announce our arrival */
 	NOTICE(FIRMWARE_WELCOME_STR);
-	NOTICE("BL1: %s\n", version_string);
+	NOTICE("BL1: %s\n", build_version_string);
 	NOTICE("BL1: %s\n", build_message);
 
 	INFO("BL1: RAM %p - %p\n", (void *)BL1_RAM_BASE, (void *)BL1_RAM_LIMIT);