linux: use O_EXCL when opening a file for write #926

Job	Run time
build-containers (debian, debian, bookworm, x86_64)	1m 2s
build-containers (fedora, fedora, 40, x86_64)	1m 54s
build (linux-gcc)	1m 36s
build-containers (alma, almalinux, 9, x86_64)	1m 44s
build (linux-clang)	1m 45s
build-containers (oracle, oraclelinux, 9, x86_64)	1m 58s
build (macos)	12m 43s
build-containers (rocky, rockylinux, 9, x86_64)	2m 0s
build (linux-i686-gcc)	1m 13s
build-containers (ubuntu, ubuntu, noble, i686)	59s
build (android)	40s
build-containers (ubuntu, ubuntu, noble, x86_64)	1m 44s
build (windows-cygwin-64)	14m 54s
build (windows-cygwin-32)	16m 0s
build (windows-msys2-64)	12m 59s
build (android-recovery, ubuntu-22.04, aarch64-linux-android32)	44s
	1h 13m 55s

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