Do not attempt to compile raw contextes when HAVE_RAW_CONTEXTS is not defined
This was failing on Debian x32 at least. No idea of why is now broken,
but trying to build simgrid v3.29 on x32 raised the cmake message
"Disable fast raw contexts on x32 ABI" and then failed with:
[ 95%] Linking CXX shared library lib/libsimgrid.so
/usr/bin/cmake -E cmake_link_script CMakeFiles/simgrid.dir/link.txt --verbose=1
(very long c++ command line, listing all .o files)
/tmp/ccRaRl4N.s: Assembler messages:
/tmp/ccRaRl4N.s:23: Error: unsupported syntax for `ret'
/tmp/ccRaRl4N.s:31: Error: invalid instruction suffix for `push'
/tmp/ccRaRl4N.s:32: Error: invalid instruction suffix for `push'
/tmp/ccRaRl4N.s:33: Error: invalid instruction suffix for `push'
/tmp/ccRaRl4N.s:34: Error: invalid instruction suffix for `push'
/tmp/ccRaRl4N.s:37: Error: invalid instruction suffix for `pop'
/tmp/ccRaRl4N.s:38: Error: invalid instruction suffix for `pop'
/tmp/ccRaRl4N.s:39: Error: invalid instruction suffix for `pop'
/tmp/ccRaRl4N.s:40: Error: invalid instruction suffix for `pop'
/tmp/ccRaRl4N.s:41: Error: unsupported syntax for `ret'
lto-wrapper: fatal error: /usr/bin/c++ returned 1 exit status
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
