ANDROID: Use more of the llvm toolchain

Where toolchain bits don't work, add some workarounds, or go back to the
old tool. Steps towards LLVM=1 for U-Boot.

This change is actually needed for RISCV because there is no legacy GCC
or binutils toolchain for that arch.

Bug: 253637149
Signed-off-by: Alistair Delva <adelva@google.com>
Change-Id: Ief9ccbeff496553e36825795dc09056340e07b56
7 files changed