[SYCL] Fix TCAndArchs leaking across offload kinds in BuildOffloadingActions (#22463)
TCAndArchs was declared outside the per-kind loop but only cleared
inside it after the bug was introduced by ccdf2c6bd7. Without the clear,
entries from prior kinds (e.g. OpenMP's spir64 TC) accumulated and were
incorrectly used when processing subsequent kinds (SYCL), causing SYCL
device actions to pick up the wrong toolchain triple.
CMPLRLLVM-76332
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>