build

Auto-detect std::string_view support by default #258

Job	Run time
ubuntu cmake	18s
windows (Win32, standard)	1m 34s
macos cmake	14s
ubuntu (g++, standard)	1m 9s
windows (Win32, PUGIXML_WCHAR_MODE)	1m 36s
ubuntu (g++, PUGIXML_WCHAR_MODE)	1m 13s
windows (Win32, PUGIXML_COMPACT)	1m 6s
ubuntu (g++, PUGIXML_COMPACT)	1m 8s
windows (Win32, PUGIXML_NO_EXCEPTIONS)	1m 35s
ubuntu (g++, PUGIXML_NO_EXCEPTIONS)	1m 4s
windows (x64, standard)	1m 30s
ubuntu (clang++, standard)	50s
windows (x64, PUGIXML_WCHAR_MODE)	1m 35s
ubuntu (clang++, PUGIXML_WCHAR_MODE)	53s
windows (x64, PUGIXML_COMPACT)	1m 8s
ubuntu (clang++, PUGIXML_COMPACT)	52s
windows (x64, PUGIXML_NO_EXCEPTIONS)	1m 5s
ubuntu (clang++, PUGIXML_NO_EXCEPTIONS)	48s
macos (clang++, standard)	43s
macos (clang++, PUGIXML_WCHAR_MODE)	46s
macos (clang++, PUGIXML_COMPACT)	58s
macos (clang++, PUGIXML_NO_EXCEPTIONS)	42s
	22m 47s

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