Use scons with python3 in the build
As D8975 got merged with Scons using python3 as the default, breaking the build of other packages, that was immediatly patched and the build was retracted.
Now this time it must invoke scons with python3 /usr/bin/scons.
Signed-off-by: Martin Reboredo <firstname.lastname@example.org>
Test Plan: Build the package.
Reviewers: Triage Team, JoshStrobl
Reviewed By: Triage Team, JoshStrobl
Differential Revision: https://dev.getsol.us/D9104