Do not let GCC use built-in functions

In order to reduce the software dependency on the compiler, the project
is now compiled with the '-ffreestanding' flag. This is to prevent GCC
from replacing functions with more optimised versions. An example is
where GCC replaces a simple printf() with a puts().

Change-Id: I1973fe6957cd708e8432a0039af9d50e037bd884
diff --git a/docs/change-log.md b/docs/change-log.md
index 08d1854..b400ac7 100644
--- a/docs/change-log.md
+++ b/docs/change-log.md
@@ -82,6 +82,9 @@
     Implementations for `putchar()` and `strchr()` were added to the local C
     library.
 
+*   GCC compiler built-in function support has been disabled in order to improve
+    compiler independence.
+
 
 ARM Trusted Firmware - version 0.2
 ==================================