Fix Longtail_OpenAppendFile on Linux #895

Job	Run time
test-linux (debug)	43s
test-linux (release)	51s
cancel-old-build	7s
build-linux (debug, static_lib)	23s
build-darwin (debug, static_lib, x64)	34s
build-linux (debug, shared_lib)	24s
build-win32 (debug, static_lib)	49s
build-linux (debug, cmd)	43s
build-darwin (debug, static_lib, arm64)	32s
build-linux (release, static_lib)	1m 21s
build-darwin (debug, shared_lib, x64)	31s
build-win32 (debug, shared_lib)	30s
build-linux (release, shared_lib)	46s
build-darwin (debug, shared_lib, arm64)	37s
build-win32 (debug, cmd)	1m 3s
build-linux (release, cmd)	48s
build-darwin (debug, cmd, x64)	45s
build-win32 (release, static_lib)	1m 48s
build-darwin (debug, cmd, arm64)	41s
build-win32 (release, shared_lib)	1m 23s
build-darwin (release, static_lib, x64)	1m 2s
build-win32 (release, cmd)	1m 23s
test-darwin (debug, arm64)	39s
build-darwin (release, static_lib, arm64)	56s
test-darwin (debug, x64)	54s
build-darwin (release, shared_lib, x64)	51s
test-darwin (release, arm64)	54s
test-win32 (debug)	46s
build-darwin (release, shared_lib, arm64)	47s
test-darwin (release, x64)	56s
test-win32 (release)	1m 41s
build-darwin (release, cmd, x64)	58s
build-darwin (release, cmd, arm64)	53s
dist-win32	15s
dist-linux	9s
dist-darwin (x64)	16s
dist-darwin (arm64)	13s
	28m 52s

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