Revert "reproducible: fix DATE/TIME macros in toolchain-wrapper"

This reverts commit 76838f63.

The commit referenced above explicitly states that the function was
copied as-is from the gcc source code at the time. And indeed that is
exactly how the function appeared in gcc in commit
e3e8c48c4a494d9da741c1c8ea6c4c0b7c4ff934.

However, our toolchain wrapper is "GPLv2 only", while the file this function
was copied from is "GPLv3 or later".  As such we can't include that function
and still comply to both licenses.

Furthermore, the code is far from optimum.

Since this feature is not release-critical, revert it until we re-implement
it.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Jérôme Pouiller <jezz@sysmic.org>
Cc: Samuel Martin <s.martin49@gmail.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>