Dotty

Fix Windows OS detection in TraceNameManglingTest #33184

Job	Run time
test	55m 21s
test_non_bootstrapped	0s
MiMa	12m 11s
test_scala2_library_tasty	0s
test_windows_fast	54m 28s
test_windows_full	1h 6m 17s
community_build_a	48m 57s
community_build_b	1h 27m 58s
community_build_c	1h 5m 44s
build-msi-package	0s
test_java8	0s
test_sbt	18m 47s
build-sdk-package / build	8m 8s
test-msi-package	0s
build-chocolatey-package / build	22s
test-chocolatey-package	0s
publish_nightly	0s
publish_release	0s
nightly_documentation	0s
open_issue_on_failure	0s
	6h 58m 13s

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