We fix several issues involving SAGE_FAT_BINARY:

• numpy intrinsics need a special build flag in this mode

• ntl needs to disable use of a problematic instruction set

• After ci-cygwin*.yml: delegate to tox, add more stages, use more specific SAGE_LOCAL #31064, the GH Actions tests for cygwin did not pass SAGE_FAT_BINARY to the actual build, randomly causing SIGILLs when a partial build was passed to the next stage through the sage-local artifact

Depends on #31493

CC: @dimpase @orlitzky @kiwifb @embray @darijgr @tscrim @kliem @seblabbe

Component: porting

Keywords: sd111

Author: Jonathan Kliem, Matthias Koeppe

Branch/Commit: d6dced2

Reviewer: Matthias Koeppe, Jonathan Kliem

Issue created by migration from https://trac.sagemath.org/ticket/29537