reproducibility: introduce config knob

Making the builds reproducible involves turning off build timestamps,
which some users may find annoying. So make the reproducible builds
optional.

Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

Config.in

@@ -728,6 +728,17 @@ config BR2_COMPILER_PARANOID_UNSAFE_PATH
 
 endmenu
 
+config BR2_REPRODUCIBLE
+	bool "Make the build reproducible (experimental)"
+        help
+          This option will remove all sources of non-reproducibility
+          from the build process. For a given Buildroot configuration,
+          this allows to generate exactly identical binaries from one
+          build to the other, including on different machines.
+
+          This is labeled as an experimental feature, as not all
+          packages behave properly to ensure reproducibility.
+
 endmenu
 
 source "toolchain/Config.in"