What are the differences bwteen clang/clang++ and "zig cc/c++"?

With

cc="clang -march=native"
cxx="clang++ -march=native"

the build also succeeded.

My notebook is old. It supports avx2 but not avx512.
The current BUILD.gn in the skia project doesn’t provide an options to disable avx512. I commented out the following lines in it but the zig compiler build still failed with the same errors.

# defines += [ "SK_ENABLE_AVX512_OPTS" ]

  deps = [
...
    #":skx",
...
  ]

After adding extra_cflags=["-DSKCMS_PORTABLE"] as gn argument, the avx errors go, but some other new errors come. The new errors look related to some definitions. Strangely, clang build doesn’t need the definitions. I stopped here.