7090968: Allow adlc register class to depend on runtime conditions
Summary: allow reg_class definition as a function.
Reviewed-by: kvn, never
os_family = linux
arch = zero
arch_model = zero
os_arch = linux_zero
os_arch_model = linux_zero
lib_arch = zero
compiler = gcc
gnu_dis_arch = zero
sysdefs = -DLINUX -D_GNU_SOURCE -DCC_INTERP -DZERO -D@ZERO_ARCHDEF@ -DZERO_LIBARCH=\"@ZERO_LIBARCH@\"