RISC-V: Define MUSL_DYNAMIC_LINKER

RISC-V: Define MUSL_DYNAMIC_LINKER

Use no suffix at all in the musl dynamic linker name for hard
float ABI. Use -sf and -sp suffixes in musl dynamic linker name
for soft float and single precision ABIs. The following table
outlines the musl interpreter names for the RISC-V ABI names.

musl interpreter        | RISC-V ABI
----------------------- | -------------
ld-musl-riscv32.so.1    | riscv32-ilp32d
ld-musl-riscv64.so.1    | riscv64-lp64d
ld-musl-riscv32-sf.so.1 | riscv32-ilp32
ld-musl-riscv64-sf.so.1 | riscv64-lp64
ld-musl-riscv32-sp.so.1 | riscv32-ilp32f
ld-musl-riscv64-sp.so.1 | riscv64-lp64f

gcc/ChangeLog

2017-11-06  Michael Clark  <michaeljclark@mac.com>

        * config/riscv/linux.h (MUSL_ABI_SUFFIX): New define.
        (MUSL_DYNAMIC_LINKER): Likewise.

From-SVN: r254500