scons: Compatibility with Scons development version string
This ensures Mesa3D build doesn't fail in this case as encountered when bisecting Scons source code while regression testing https://bugs.freedesktop.org/show_bug.cgi?id=109443 and when testing 3.0.5.a.2
Technical details: Scons version string has consistently been in this format: MajorVersion.MinorVersion.Patch[.alpha/beta.yyyymmdd] so these formulas should strip alpha/beta flags and return Scons version:
- as string -
- as tuple of integers -
v2: Fixed Scons version retrieval formulas as string and tuple of integers.
v3: Fixed Scons version string format description.
Cc: "19.0" firstname.lastname@example.org