Revert "meta-ohos-core: toolchain: Switch defaults to use clang, compiler-rt and libc++"

This reverts commit a07e1f56.

Forum: https://forum.ostc-eu.org/t/reverting-compiler-back-to-gcc/76/3


Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>