Add explanatory comment to fuzzer build files

This change adds a comment related to the use of host_toolchain to
account for cross compilation, and removes a print statement that had
been accidentally left in a build script.

Bug: tint:966
Change-Id: I6334225864632d9983ab197bb28fcb972d5ba1d4
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/58000
Auto-Submit: Alastair Donaldson <afdx@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

fuzzers/generate_spirv_corpus.py

@@ -49,7 +49,6 @@ def main():
     input_dir: str = os.path.abspath(sys.argv[1].rstrip(os.sep))
     corpus_dir: str = os.path.abspath(sys.argv[2])
     spirv_as_path: str = os.path.abspath(sys.argv[3])
-    print(' '.join([input_dir, corpus_dir, spirv_as_path]))
     if os.path.exists(corpus_dir):
         shutil.rmtree(corpus_dir)
     os.makedirs(corpus_dir)