Don't use F_OK constant which is not defined on Windows

The MS documentation for the access() function only list numerical constants.
2 jobs for master in 8 minutes and 40 seconds (queued for 1020 minutes and 25 seconds)
Status Job ID Name Coverage
  Build
failed #76297
build_clazy_clang_tidy

00:04:33

passed #76296
linux kf5-qt5 qt5.14

00:04:07

0.0%
 
Name Stage Failure
failed
build_clazy_clang_tidy Build
-- Configuring incomplete, errors occurred!
See also "/builds/pim/libkleo/build/CMakeFiles/CMakeOutput.log".
See also "/builds/pim/libkleo/build/CMakeFiles/CMakeError.log".
Uploading artifacts for failed job
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WARNING: JUnitTestResults.xml: no matching files
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Cleaning up file based variables
ERROR: Job failed: exit code 1