[PATCH V2] tcmode-default.inc: use ?= to set PREFERRED_VERSION_llvm/llvm-native/nativesdk-llvm

[<changqing.li@windriver.com>]

From: Changqing Li <changqing.li@windriver.com>

If meta-clang is included, LLVMVERSION might set to version different
from llvm version in oe-core, and PREFERRED_PROVIDER_llvm set to clang,
In this condition, following warning is reported:
WARNING: preferred version 16.0.1 of llvm-native not available (for item llvm-native)
WARNING: versions of llvm-native available: 15.0.7

use ?= to set following configs in order to allow user
to override the default settings:
PREFERRED_VERSION_llvm
PREFERRED_VERSION_llvm-native
PREFERRED_VERSION_nativesdk-llvm

Signed-off-by: Changqing Li <changqing.li@windriver.com>
---
 meta/conf/distro/include/tcmode-default.inc | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/meta/conf/distro/include/tcmode-default.inc b/meta/conf/distro/include/tcmode-default.inc
index 3720a4c5b8..0de858d3af 100644
--- a/meta/conf/distro/include/tcmode-default.inc
+++ b/meta/conf/distro/include/tcmode-default.inc
@@ -77,9 +77,9 @@ PREFERRED_VERSION_go-runtime ?= "${GOVERSION}"
 PREFERRED_VERSION_nativesdk-go ?= "${GOVERSION}"
 PREFERRED_VERSION_nativesdk-go-runtime ?= "${GOVERSION}"
 
-PREFERRED_VERSION_llvm = "${LLVMVERSION}"
-PREFERRED_VERSION_llvm-native = "${LLVMVERSION}"
-PREFERRED_VERSION_nativesdk-llvm = "${LLVMVERSION}"
+PREFERRED_VERSION_llvm ?= "${LLVMVERSION}"
+PREFERRED_VERSION_llvm-native ?= "${LLVMVERSION}"
+PREFERRED_VERSION_nativesdk-llvm ?= "${LLVMVERSION}"
 
 # Rust toolchain preferred versions:
 
-- 
2.25.1