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/plat/imx/common/imx_sip_handler.c b/plat/imx/common/imx_sip_handler.c
index 5d29186..49fdacf 100644
--- a/plat/imx/common/imx_sip_handler.c
+++ b/plat/imx/common/imx_sip_handler.c
@@ -9,9 +9,10 @@
 #include <stdint.h>
 #include <services/std_svc.h>
 #include <string.h>
-#include <platform_def.h>
+#include <common/build_message.h>
 #include <common/debug.h>
 #include <common/runtime_svc.h>
+#include <platform_def.h>
 #include <imx_sip_svc.h>
 #include <lib/el3_runtime/context_mgmt.h>
 #include <lib/mmio.h>
@@ -261,7 +262,7 @@
 		    u_register_t x4)
 {
 	/* Parse the version_string */
-	char *parse = (char *)version_string;
+	char *parse = (char *)build_version_string;
 	uint64_t hash = 0;
 
 	do {