RISC-V: testsuite: Fix strcmp-run.c test.
This fixes expectations in the strcmp-run test which would sometimes
fail with newlib. The test expects libc strcmp return values and
asserts the vectorized result is similar to those. Therefore hard-code
the expected results instead of relying on a strcmp call.
gcc/testsuite/ChangeLog:
* gcc.target/riscv/rvv/autovec/builtin/strcmp-run.c: Adjust test
expectation and target selector.
* gcc.target/riscv/rvv/autovec/builtin/strlen-run.c: Adjust
target selector.
* gcc.target/riscv/rvv/autovec/builtin/strncmp-run.c: Ditto.