Fix alloca undefined on Solaris
Solaris defines alloca in the <alloca.h> header
../src/cairo-colr-glyph-render.c: In function ‘add_sweep_gradient_patches’:
../src/cairo-colr-glyph-render.c:661:14: error: implicit declaration of
function ‘alloca’ [-Werror=implicit-function-declaration]
661 | angles = alloca (sizeof (double) * cl->n_stops);
| ^~~~~~
Signed-off-by: Alan Coopersmith alan.coopersmith@oracle.com