Make:Use environment variables for OS detection.
Add make helper files to select the appropriate settings for the build
environment. Selection is made in make_helpers/build_env.mk, which
selects other files to include using generic build environment settings.
The Trusted Firmware Makefile and supporting tool Makefiles are updated
to include build_env.mk instead of unix.mk.
NOTE: This change does not fully enable builds in other build
environments. It facilitates this without compromising the
existing build environments.
Change-Id: Ic4064ffe6ce158bbd16d7cc9f27dd4655a3580f6
diff --git a/Makefile b/Makefile
index 8502e2e..1eb0174 100644
--- a/Makefile
+++ b/Makefile
@@ -39,7 +39,7 @@
MAKE_HELPERS_DIRECTORY := make_helpers/
include ${MAKE_HELPERS_DIRECTORY}build_macros.mk
-include ${MAKE_HELPERS_DIRECTORY}unix.mk
+include ${MAKE_HELPERS_DIRECTORY}build_env.mk
################################################################################
# Default values for build configurations