When we build a copr image, we run the "nm-copr-build.sh" script.
That script, should honor "LTO=0|1|" to explicitly enable/disable
LTO. Since the copr script only builds a SRPM, which then gets build
we need that the default LTO flag in the SRPM is templated.
Fixes: 0566e9dc63 ('contrib: support disabling "LTO" in "nm-copr-build.sh"')
(cherry picked from commit 096b9955d6)
The "nm-copr-build.sh" script is run by our copr to generate the SRPM of
NetworkManager (via `curl ... | bash`).
Building with LTO takes a long time, for testing it can be nice to disable
that. Add an environment variable for that. It can be used when manually
building an RPM in copr.
(cherry picked from commit 0566e9dc63)
