219 use debug log level by default #541

Job	Run time
B2 gcc-11	4m 57s
CMake gcc-11 17 Debug	8m 53s
B2 msvc-14.2	8m 36s
B2 clang-14	5m 16s
CMake gcc-11 20 Release	11m 34s
CMake msvc-14.2 Debug C++17	7m 48s
B2 msvc-14.3	6m 58s
CMake clang-11 17 Debug	6m 6s
CMake msvc-14.2 Release C++17	7m 6s
CMake clang-11 20 Debug	6m 33s
CMake msvc-14.3 Debug C++20	6m 14s
CMake clang-13 17 Release	9m 21s
CMake msvc-14.3 Release C++20	6m 26s
CMake clang-13 20 Release	9m 47s
CMake clang-14 17 Debug -stdlib=libc++	7m 57s
CMake clang-14 20 Release -stdlib=libc++	11m 46s
	2h 5m 18s

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