Provide an 'auto' option for --line_terminator #5033

Job	Run time
x86_64 test	2m 21s
CheckFormatAndBuildClean	1m 54s
arm64 test	2m 22s
KytheVerification	0s
ClangTidy	2m 28s
x86_64 test-clang	2m 18s
arm64 test-clang	2m 19s
KytheXrefs	2m 17s
MacOsBuild	1m 16s
x86_64 test-nortti	2m 22s
📦 Pack Sources	6s
x86_64 test-c++20	2m 12s
PrepareVSPlugin	2m 22s
x86_64 test-c++23	2m 10s
WindowsBuild	1m 35s
x86_64 smoke-test	2m 22s
arm64 smoke-test	2m 24s
x86_64 asan	2m 24s
x86_64 asan-clang	2m 17s
x86_64 compile	2m 23s
arm64 compile	2m 24s
x86_64 compile-clang	2m 25s
arm64 compile-clang	2m 22s
x86_64 compile-static	2m 24s
arm64 compile-static	2m 23s
x86_64 compile-static-clang	2m 24s
arm64 compile-static-clang	2m 21s
x86_64 clean	2m 18s
arm64 clean	2m 24s
📦 Release	1s
Build and deploy GitHub pages	1s
	1h 1m 19s

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