[Fuchsia][CMake] Check correct triple to set -mcpu (#101910)

We use armv8m.main-none-eabi now, not armv8m.main-unknown-eabi.

Author: petrhosek

clang/cmake/caches/Fuchsia-stage2.cmake

@@ -328,7 +328,7 @@ foreach(target armv6m-none-eabi;armv7m-none-eabi;armv8m.main-none-eabi)
     # TODO: The preprocessor defines workaround various issues in libc and libc++ integration.
     # These should be addressed and removed over time.
     set(RUNTIMES_${target}_CMAKE_${lang}_local_flags "--target=${target} -mthumb -Wno-atomic-alignment \"-Dvfprintf(stream, format, vlist)=vprintf(format, vlist)\" \"-Dfprintf(stream, format, ...)=printf(format)\" \"-Dtimeval=struct timeval{int tv_sec; int tv_usec;}\" \"-Dgettimeofday(tv, tz)\" -D_LIBCPP_PRINT=1")
-    if(${target} STREQUAL "armv8m.main-unknown-eabi")
+    if(${target} STREQUAL "armv8m.main-none-eabi")
       set(RUNTIMES_${target}_CMAKE_${lang}_local_flags "${RUNTIMES_${target}_CMAKE_${lang}_local_flags} -mfloat-abi=softfp -march=armv8m.main+fp+dsp -mcpu=cortex-m33" CACHE STRING "")
     endif()
     set(RUNTIMES_${target}_CMAKE_${lang}_FLAGS "${RUNTIMES_${target}_CMAKE_${lang}_local_flags}" CACHE STRING "")