riscv: fix riscv64sf build

The library needs to have sf suffix cut off.

MFC after:	3 days
X-MFC with:	3781e77995
Differential revision:	https://reviews.freebsd.org/D34561
Reviewed by:	dim

lib/libclang_rt/compiler-rt-vars.mk

@@ -8,7 +8,7 @@ SANITIZER_LIBDIR=		${CLANGDIR}/lib/freebsd
     (!defined(CPUTYPE) || ${CPUTYPE:M*soft*} == "")
 CRTARCH?=	armhf
 .else
-CRTARCH?=	${MACHINE_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}
+CRTARCH?=	${MACHINE_ARCH:S/amd64/x86_64/:C/hf$//:C/sf$//:S/mipsn32/mips64/}
 .endif
 
 .if ${COMPILER_TYPE} == "clang"