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/common/bl_common.c b/common/bl_common.c
index 8fce02f..fe4de0a 100644
--- a/common/bl_common.c
+++ b/common/bl_common.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2022, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2024, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -12,6 +12,7 @@
 #include <arch_features.h>
 #include <arch_helpers.h>
 #include <common/bl_common.h>
+#include <common/build_message.h>
 #include <common/debug.h>
 #include <drivers/auth/auth_mod.h>
 #include <drivers/io/io_storage.h>
@@ -275,6 +276,5 @@
  */
 const char *get_version(void)
 {
-	extern const char version[];
-	return version;
+	return build_version;
 }