package/optee-test: new package

package/optee-test: new package

OP-TEE test package provide test materials as part of the OP-TEE
project helping platforms to verify their OP-TEE components
against a set of regression and performance tests.

Package is added in the BR package configuration next to the
OP-TEE client package.

This change references in Buildroot the today's latest OP-TEE
revision release tagged 3.4.0 with an added patch to fix an issue
reported by recent GCC toolchains.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
[Thomas:
 - drop version selection
 - propagate !BR2_STATIC_LIBS dependency of optee-client
 - make sure BR2_TARGET_OPTEE_OS_SDK is selected
 - use a patch generated by git format-patch
 - simplify the construct to build the examples]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>