autoconf: Sanitize asm build for cross-compiling and --enable-*-bit
autoconf: Sanitize asm build for cross-compiling and --enable-*-bit

Two fixes to the asm configuration:
 - Disable when the user is cross-compiling for x86 or x86_64 since it
   requires running an executable compiled for the target host.
 - If the user has specified --enable-32-bit on x86_64 or --enable-64-bit
   on x86, respect that and choose the correct asm architecture.

benaadams/glsl-optimizer,dellis1972/glsl-optimizer,tokyovigilante/glsl-optimizer,mcanthony/glsl-optimizer,wolf96/glsl-optimizer,mcanthony/glsl-optimizer,zeux/glsl-optimizer,benaadams/glsl-optimizer,mapbox/glsl-optimizer,wolf96/glsl-optimizer,zz85/glsl-optimizer,dellis1972/glsl-optimizer,tokyovigilante/glsl-optimizer,KTXSoftware/glsl2agal,mapbox/glsl-optimizer,djreep81/glsl-optimizer,mcanthony/glsl-optimizer,wolf96/glsl-optimizer,benaadams/glsl-optimizer,bkaradzic/glsl-optimizer,mapbox/glsl-optimizer,dellis1972/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,adobe/glsl2agal,djreep81/glsl-optimizer,adobe/glsl2agal,zeux/glsl-optimizer,tokyovigilante/glsl-optimizer,KTXSoftware/glsl2agal,mcanthony/glsl-optimizer,bkaradzic/glsl-optimizer,benaadams/glsl-optimizer,benaadams/glsl-optimizer,KTXSoftware/glsl2agal,tokyovigilante/glsl-optimizer,bkaradzic/glsl-optimizer,zeux/glsl-optimizer,djreep81/glsl-optimizer,jbarczak/glsl-optimizer,metora/MesaGLSLCompiler,bkaradzic/glsl-optimizer,KTXSoftware/glsl2agal,metora/MesaGLSLCompiler,mapbox/glsl-optimizer,adobe/glsl2agal,jbarczak/glsl-optimizer,djreep81/glsl-optimizer,zz85/glsl-optimizer,mapbox/glsl-optimizer,zeux/glsl-optimizer,tokyovigilante/glsl-optimizer,adobe/glsl2agal,zz85/glsl-optimizer,zz85/glsl-optimizer,wolf96/glsl-optimizer,djreep81/glsl-optimizer,mcanthony/glsl-optimizer,jbarczak/glsl-optimizer,metora/MesaGLSLCompiler,benaadams/glsl-optimizer,wolf96/glsl-optimizer,dellis1972/glsl-optimizer,zeux/glsl-optimizer,adobe/glsl2agal,jbarczak/glsl-optimizer,KTXSoftware/glsl2agal,zz85/glsl-optimizer,jbarczak/glsl-optimizer,bkaradzic/glsl-optimizer