clang: Disable unused-command-line-argument warning for debug builds

This ensures that nativesdk compiler can be built when
DEBUG_BUILD = "1"

Fixes #932

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

recipes-devtools/clang/clang_git.bb

@@ -15,6 +15,9 @@ BUILD_CXX:class-nativesdk = "clang++"
 BUILD_AR:class-nativesdk = "llvm-ar"
 BUILD_RANLIB:class-nativesdk = "llvm-ranlib"
 BUILD_NM:class-nativesdk = "llvm-nm"
+
+BUILDSDK_CPPFLAGS:append:class-nativesdk = "${@oe.utils.vartrue('DEBUG_BUILD', ' -Wno-error=unused-command-line-argument', '', d)}"
+
 LDFLAGS:remove:class-nativesdk = "-fuse-ld=lld"
 
 LDFLAGS:append:class-target:riscv32 = " -Wl,--no-as-needed -latomic -Wl,--as-needed"