aom: prevent use of RISC-V intrinsics

Cross-compilation fails since v3.13.0
Investigate later, this platform is low priority

Author: lovell

build/posix.sh

@@ -178,7 +178,7 @@ cd aom_build
 AOM_AS_FLAGS="${FLAGS}" cmake -G"Unix Makefiles" \
   -DCMAKE_TOOLCHAIN_FILE=${ROOT}/Toolchain.cmake -DCMAKE_INSTALL_PREFIX=${TARGET} -DCMAKE_INSTALL_LIBDIR=lib -DCMAKE_BUILD_TYPE=MinSizeRel \
   -DBUILD_SHARED_LIBS=FALSE -DENABLE_DOCS=0 -DENABLE_TESTS=0 -DENABLE_TESTDATA=0 -DENABLE_TOOLS=0 -DENABLE_EXAMPLES=0 \
-  -DCONFIG_PIC=1 -DENABLE_NASM=1 ${WITHOUT_NEON:+-DENABLE_NEON=0} \
+  -DCONFIG_PIC=1 -DENABLE_NASM=1 ${WITHOUT_NEON:+-DENABLE_NEON=0} -DENABLE_RVV=0 \
   -DCONFIG_AV1_HIGHBITDEPTH=0 -DCONFIG_WEBM_IO=0 \
   ..
 make install/strip