clang.bbclass: Limit using clang to target recipes only

since toolchain-clang maybe available for native as well now, it means
we have to ensure we do not use it for native recipes _yet_

Signed-off-by: Khem Raj <raj.khem@gmail.com>

classes/clang.bbclass

@@ -1,13 +1,13 @@
 # Add the necessary override
-CCACHE_COMPILERCHECK_toolchain-clang ?= "%compiler% -v"
-HOST_CC_ARCH_prepend_toolchain-clang = "-target ${HOST_SYS} "
-CC_toolchain-clang  = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
-CXX_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang++ ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
-CPP_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS} -E"
-CCLD_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
-RANLIB_toolchain-clang = "${HOST_PREFIX}llvm-ranlib"
-AR_toolchain-clang = "${HOST_PREFIX}llvm-ar"
-NM_toolchain-clang = "${HOST_PREFIX}llvm-nm"
+CCACHE_COMPILERCHECK_class-target_toolchain-clang ?= "%compiler% -v"
+HOST_CC_ARCH_prepend_class-target_toolchain-clang = "-target ${HOST_SYS} "
+CC_class-target_toolchain-clang  = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
+CXX_class-target_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang++ ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
+CPP_class-target_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS} -E"
+CCLD_class-target_toolchain-clang = "${CCACHE}${HOST_PREFIX}clang ${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}"
+RANLIB_class-target_toolchain-clang = "${HOST_PREFIX}llvm-ranlib"
+AR_class-target_toolchain-clang = "${HOST_PREFIX}llvm-ar"
+NM_class-target_toolchain-clang = "${HOST_PREFIX}llvm-nm"
 
 LTO_toolchain-clang = "${@bb.utils.contains('DISTRO_FEATURES', 'thin-lto', '-flto=thin', '-flto -fuse-ld=lld', d)}"
 PACKAGE_DEBUG_SPLIT_STYLE_toolchain-clang = "debug-without-src"