Remove redundant `-o` flag #988

Job	Run time
macos-static	2m 27s
windows (32, windows-2019)	5m 16s
unix (ubuntu-20.04, g++, make)	5m 30s
windows-mingw-build (32)	56s
windows (32, windows-2022)	6m 0s
unix (ubuntu-20.04, g++, cmake)	5m 15s
windows-mingw-build (64)	58s
windows (64, windows-2019)	4m 18s
unix (ubuntu-20.04, clang++, make)	6m 6s
windows (64, windows-2022)	6m 14s
unix (ubuntu-20.04, clang++, cmake)	5m 47s
unix (ubuntu-22.04, g++, make)	6m 3s
unix (ubuntu-22.04, g++, cmake)	5m 46s
unix (ubuntu-22.04, clang++, make)	4m 22s
unix (ubuntu-22.04, clang++, cmake)	3m 54s
unix (macos-14, clang++, make)	8m 7s
unix (macos-14, clang++, cmake)	6m 10s
windows-mingw-testing (windows-2019, 32)	4m 9s
windows-mingw-testing (windows-2019, 64)	4m 10s
windows-mingw-testing (windows-2022, 32)	5m 1s
windows-mingw-testing (windows-2022, 64)	4m 38s
	1h 41m 7s

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