Merge bitcoin/bitcoin#32209: test: Preserve llvm profile path

c5a7ffd preserve llvm profile env (Prabhat Verma)

Pull request description:

  While generating `profraw` for fuzz tests using steps in [PR 32206](bitcoin/bitcoin#32206) , the profraw was not being built at the desired location and only one `default.profraw` was being created which was being overwritten for multiple fuzz targets. This PR fixes that.

ACKs for top commit:
  maflcko:
    lgtm ACK c5a7ffd
  mabu44:
    ACK c5a7ffd

Tree-SHA512: 11f74caa8cba6f841aa899a5e294f658aed1b6a3d4cf68992609ea99fadb4a092b2350ffacea5c2d5eb377eb10082de018f27a1d6486a72460cb3905aaa15664

Author: fanquake

test/fuzz/test_runner.py

@@ -11,15 +11,14 @@
 import configparser
 import logging
 import os
-import platform
 import random
 import subprocess
 import sys
 
 
 def get_fuzz_env(*, target, source_dir):
     symbolizer = os.environ.get('LLVM_SYMBOLIZER_PATH', "/usr/bin/llvm-symbolizer")
-    fuzz_env = {
+    fuzz_env = os.environ | {
         'FUZZ': target,
         'UBSAN_OPTIONS':
         f'suppressions={source_dir}/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1',
@@ -28,9 +27,6 @@ def get_fuzz_env(*, target, source_dir):
         'ASAN_SYMBOLIZER_PATH': symbolizer,
         'MSAN_SYMBOLIZER_PATH': symbolizer,
     }
-    if platform.system() == "Windows":
-        # On Windows, `env` option must include valid `SystemRoot`.
-        fuzz_env = {**fuzz_env, 'SystemRoot': os.environ.get('SystemRoot')}
     return fuzz_env