!15 Add toolchain_clang build support

From: @liyunfei33 
Reviewed-by: @cf-zhao 
Signed-off-by: @cf-zhao

lld.spec

@@ -1,5 +1,10 @@
 %bcond_without sys_llvm
 %bcond_without check
+%bcond_without toolchain_clang
+
+%if %{with toolchain_clang}
+%global toolchain clang
+%endif
 
 %global maj_ver 17
 %global min_ver 0
@@ -32,7 +37,7 @@
 
 Name:		%{pkg_name}
 Version:	%{maj_ver}.%{min_ver}.%{patch_ver}
-Release:	2
+Release:	3
 Summary:	The LLVM Linker
 
 License:	NCSA
@@ -104,6 +109,10 @@ cd _build
 	-DLLVM_LIT_ARGS="-sv \
 	--path %{install_prefix}" \
 	-DLLVM_COMMON_CMAKE_UTILS=%{install_datadir}/llvm/cmake \
+%if "%{toolchain}" == "clang"
+	-DCMAKE_C_COMPILER=clang \
+	-DCMAKE_CXX_COMPILER=clang++ \
+%endif
 	-DLLVM_MAIN_SRC_DIR=%{install_prefix}/src
 
 %ninja_build
@@ -131,6 +140,9 @@ rm %{buildroot}%{install_includedir}/mach-o/compact_unwind_encoding.h
 %{install_libdir}/liblld*.so.*
 
 %changelog
+* Fri Jul 5 2024 liyunfei <liyunfei33@huawei.com> - 17.0.6-3
+- Add toolchain_clang build support
+
 * Mon Mar 25 2024 zhanglimin <zhanglimin@loongson.cn> - 17.0.6-2
 - Supoort `relax` feature on LoongArch