The Modules/getbuildinfo.c allows the use of DATE and TIME
macros to be defined via CFLAGS.
These vars, control the build date & time when the
interpreter is opened, and can be read via the
`platform._sys_version()` function.
So, a conversion from SOURCE_DATE_EPOCH to DATE & TIME
is required at build-time.
This is especially needed for `platform._sys_version()`
to work.
The installation of pip seems to rely on this.
The logic has been adapted from:
https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal#Makefile
Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>
