[committed] [RISC-V] Don't run new rounding tests on newlib risc-v targets

[committed] [RISC-V] Don't run new rounding tests on newlib risc-v targets

The new round_32.c and round_64.c tests depend on the optimizers to recognize
the conversions feeding the floor/ceil calls and convert them into ceilf,
floorf and the like.

Those transformations only occur when the target indicates the C library has
the appropriate routines (fnclass == function_c99_misc).  While newlib has
these routines, they are not exposed as available to the compiler and thus the
transformation the tests depend on do not happen. Naturally the scan-tests then
fail.

gcc/testsuite
	* gcc.target/riscv/round_32.c: Add require-effective-target glibc.
	* gcc.target/riscv/round_64.c: Likewise.