Fixes in-tree build when the script is called as "win32/build.py"
and not "./win32/build.py".

Fixes in-tree build when the script is called as "android/build.py"
and not "./android/build.py".

The Linux feature allows writing new files to an invisible file, and
then replace the old file.  This preserves the old file if we get
interrupted by some event.

Fixes a problem with the "curl" input plugin: IsEOF() always returns
true because the "open" flag was cleared by
CurlInputStream::RequestDone() when end-of-stream was reached.  This
flag stays false even when seeking to another position has succeeded.

This patch resets the "open" flag to true after seeking successfully.