arm/optee: clean up OPTEE_COMPILER assignment

Now that clang is part of oe-core we can't use meta-clang being present
as an indicator of clang being available.

This does mean we can clean up the logic and just use TOOLCHAIN, as that
is always set now.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/recipes-security/optee/optee.inc

@@ -16,15 +16,13 @@ OPTEE_ARCH:arm = "arm32"
 OPTEE_ARCH:aarch64 = "arm64"
 OPTEE_CORE = "${@d.getVar('OPTEE_ARCH').upper()}"
 
-OPTEE_TOOLCHAIN = "${@d.getVar('TOOLCHAIN') or 'gcc'}"
-OPTEE_COMPILER = "${@bb.utils.contains("BBFILE_COLLECTIONS", "clang-layer", "${OPTEE_TOOLCHAIN}", "gcc", d)}"
-
 # Set here but not passed to EXTRA_OEMAKE by default as that breaks
 # the optee-os build
 TA_DEV_KIT_DIR = "${STAGING_INCDIR}/optee/export-user_ta"
 
+# Assume that our TOOLCHAIN matches OP-TEE's COMPILER
 EXTRA_OEMAKE += "V=1 \
-                 COMPILER=${OPTEE_COMPILER} \
+                 COMPILER=${TOOLCHAIN} \
                  OPTEE_CLIENT_EXPORT=${STAGING_DIR_HOST}${prefix} \
                  TEEC_EXPORT=${STAGING_DIR_HOST}${prefix} \
                 "