Don’t set SWIFT_BUILD_SCRIPT_ENVIRONMENT when building swift-format

Setting `SWIFT_BUILD_SCRIPT_ENVIRONMENT` entails that we e.g. enable assertions in swift-syntax, even in release mode, which we don’t want since the copy of swift-format that we include in the toolchain is also built using this script and shouldn’t have these swift-syntax’s assertions enabled, to improve performance.

Author: ahoppen

build-script-helper.py

@@ -176,10 +176,7 @@ def get_swiftpm_options(package_path, build_path, multiroot_data_file, configura
   return args
 
 def get_swiftpm_environment_variables(no_local_deps):
-  # Tell SwiftSyntax that we are building in a build-script environment so that
-  # it does not need to be rebuilt if it has already been built before.
   env = dict(os.environ)
-  env['SWIFT_BUILD_SCRIPT_ENVIRONMENT'] = '1'
   if not no_local_deps:
     env['SWIFTCI_USE_LOCAL_DEPS'] = "1"
   return env