This allows us to supply gcc-9 as an optional argument to cross-gcc,
successfully constructing gcc-9-based cross-compilers.
* gnu/packages/gcc.scm (gcc-9)[source](patches): Add
"gcc-9-asan-fix-limits-include.patch".
* gnu/packages/patches/gcc-9-asan-fix-limits-include.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add the patch.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>
