Revert "Let's try it"

This reverts commit 07e0cd46e16cd432c51c427a6ea4b1ff3f71fd4a.
build: Allow building with OpenJDK

My local builds with OpenJDK have been successful - no
reason to disallow it, let's go free...

Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
build/core: Add linaro_compilerchecks.mk

Add linaro_compilerchecks.mk, allowing to run some checks on the
compiler version and supported flags before setting them

Change-Id: I96e1277e74c0ea3457677bef39644aaece01f653
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
build/core: Include linaro_compilerchecks.mk

Include linaro_compilerchecks.mk in core/config.mk to allow the macros
to be used in board configs

Change-Id: I3a0dfd0a3a1c09961e43ef8c2f3cbe50b8c00e20
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>
build/core: Use better default compiler flags

Use -O3 for the compiler, -O2 for the linker

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
build: Don't work around cortex-a8 issues when targeting a9 only

Don't work around cortex-a8 issues when other compiler flags
show we want to target cortex-a9 only

Change-Id: If5a077243fc15298fbcbe2ffc857b5e961dd29da
Signed-off-by: Bernhard Rosenkraenzer <Bernhard.Rosenkranzer@linaro.org>