Allow to override the default idle timeout with an environment variable
Allow to override the default idle timeout with an environment variable

While the default is reasonable for developers, CI environment may want
to choose larger timeouts, or to disable it entirely.

The new SCCACHE_IDLE_TIMEOUT environment variable allows to pass a value
in seconds for the idle timeout before shutdown, and a value of 0
disables the timeout entirely.

glandium/sccache,luser/sccache2,glandium/sccache,luser/sccache2,mozilla/sccache,glandium/sccache,glandium/sccache,mozilla/sccache,mozilla/sccache,luser/sccache2,luser/sccache2