Merge pull request swiftlang#79174 from edymtt/edymtt/match-verbosity-of-new-stdlib-and-compiler

build-script-impl: propagate `--verbose-build` to nested CMake builds

Author: edymtt

utils/swift_build_support/swift_build_support/build_script_invocation.py

@@ -552,6 +552,11 @@ def convert_to_impl_arguments(self):
                 impl_env["HOST_VARIABLE_{}__{}".format(
                     host_target.replace("-", "_"), name)] = value
 
+        if args.verbose_build:
+            # This ensures all CMake builds (including the ones
+            # called with `ExternalProject`) have verbose output
+            impl_env["VERBOSE"] = "1"
+
         return (impl_env, impl_args)
 
     def compute_host_specific_variables(self):