Remove assumption since it breaks building --without-headers

--- gcc-4_1-branch/gcc/config/cris/t-linux
+++ gcc-4_1-branch/gcc/config/cris/t-linux
@@ -1,6 +1,2 @@
 TARGET_LIBGCC2_CFLAGS += -fPIC
 CRTSTUFF_T_CFLAGS_S = $(TARGET_LIBGCC2_CFLAGS)
-
-# We *know* we have a limits.h in the glibc library, with extra
-# definitions needed for e.g. libgfortran.
-LIMITS_H_TEST = :