arm/optee-ftpm: enable clang compilation

Remove the forcing of GCC in the recipe, and make the changes necessary
to get clang working.

Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/recipes-security/optee-ftpm/optee-ftpm_4.7.0.bb

@@ -8,9 +8,6 @@ COMPATIBLE_MACHINE:qemuarm64 = "qemuarm64"
 COMPATIBLE_MACHINE:qemuarm64-secureboot = "qemuarm64"
 COMPATIBLE_MACHINE:qemuarm-secureboot = "qemuarm"
 
-#FIXME - doesn't currently work with clang
-TOOLCHAIN = "gcc"
-
 inherit deploy python3native
 
 LICENSE = "MIT"
@@ -18,6 +15,7 @@ LIC_FILES_CHKSUM = "file://LICENSE;md5=5a3925ece0806073ae9ebbb08ff6f11e"
 LIC_FILES_CHKSUM += "file://optee-ta/LICENSE;md5=5a3925ece0806073ae9ebbb08ff6f11e"
 
 DEPENDS = "python3-pyelftools-native optee-os-tadevkit python3-cryptography-native"
+DEPENDS:append:toolchain-clang = " lld-native"
 
 FTPM_UUID = "bc50d971-d4c9-42c4-82cb-343fb7f37896"
 
@@ -49,6 +47,7 @@ TEEC_EXPORT = "${STAGING_DIR_HOST}${prefix}"
 TA_DEV_KIT_DIR = "${STAGING_INCDIR}/optee/export-user_ta"
 
 EXTRA_OEMAKE += '\
+    COMPILER=${TOOLCHAIN} \
     TA_DEV_KIT_DIR=${TA_DEV_KIT_DIR} \
     CROSS_COMPILE=${TARGET_PREFIX} \
     CFG_MS_TPM_20_REF="${S}" \
@@ -59,6 +58,8 @@ EXTRA_OEMAKE:append:aarch64:qemuall = "\
     CFG_ARM64_ta_arm64=y \
 "
 
+CFLAGS:append:toolchain-clang = " -Wno-unknown-warning-option"
+
 # python3-cryptography needs the legacy provider, so set OPENSSL_MODULES to the
 # right path until this is relocated automatically.
 export OPENSSL_MODULES = "${STAGING_LIBDIR_NATIVE}/ossl-modules"