All client version information is moved to version.cpp, which optionally
(-DHAVE_BUILD_INFO) includes build.h. build.h is automatically generated
on supporting platforms via contrib/genbuild.sh, using git describe.
The git export-subst attribute is used to put the commit id statically
in version.cpp inside generated archives, and this value is used if no
build.h is present.
The gitian descriptors are modified to use git archive instead of a
copy, to create the src/ directory in the output. This way,
src/src/version.cpp will contain the static commit id. To prevent
gitian builds from getting the "-dirty" marker in their git-describe
generated identifiers, no touching of files or running sed on the
makefile is performed anymore. This does not seem to influence
determinism.
It could just as well be on either part of the gitian build, but to safely put it on the Qt side would require bumping the filename, and every gitian user rebuilding it.
v0.5.3.1 put it on the Bitcoin side, and this is easier to work with and keep safe, so I'm moving it.
Use `qmake MINGW_THREAD_BUGFIX=0` to disable
