There are a few instances of the error below. It looks like upstream v8 has patched some riscv issues recently.
FAILED: obj/deps/v8/src/compiler/backend/v8_compiler.jump-threading.o
riscv64-unknown-linux-musl-g++ -MMD -MF obj/deps/v8/src/compiler/backend/v8_compiler.jump-threading.o.d -D_GLIBCXX_USE_CXX11_ABI=1 -D_FILE_OFFSET_BITS=64 -DNODE_OPENSSL_CONF_NAME=nodejs_conf -DNODE_OPENSSL_CERT_STORE -DICU_NO_USER_DATA_OVERRIDE -DV8_GYP_BUILD -DV8_TYPED_ARRAY_MAX_SIZE_IN_HEAP=64 -D__STDC_FORMAT_MACROS -DV8_TARGET_ARCH_RISCV64 -D__riscv_xlen=64 -DCAN_USE_FPU_INSTRUCTIONS -DV8_HAVE_TARGET_OS -DV8_TARGET_OS_LINUX '-DV8_EMBEDDER_STRING="-node.16"' -DENABLE_DISASSEMBLER -DV8_PROMISE_INTERNAL_FIELD_COUNT=1 -DV8_ENABLE_PRIVATE_MAPPING_FORK_OPTIMIZATION -DOBJECT_PRINT -DV8_INTL_SUPPORT -DV8_ATOMIC_OBJECT_FIELD_WRITES -DV8_ENABLE_LAZY_SOURCE_POSITIONS -DV8_USE_SIPHASH -DNDEBUG -DV8_WIN64_UNWINDING_INFO -DV8_ENABLE_REGEXP_INTERPRETER_THREADED_DISPATCH -DV8_USE_ZLIB -DV8_ENABLE_LEAPTIERING -DV8_ENABLE_SPARKPLUG -DV8_ENABLE_TURBOFAN -DV8_ENABLE_WEBASSEMBLY -DV8_ENABLE_JAVASCRIPT_PROMISE_HOOKS -DV8_ENABLE_CONTINUATION_PRESERVED_EMBEDDER_DATA -DV8_ALLOCATION_FOLDING -DV8_ALLOCATION_SITE_TRACKING -DV8_ADVANCED_BIGINT_ALGORITHMS -I../../deps/v8 -I../../deps/v8/include -Igen/generate-bytecode-output-root -Igen -I../../deps/v8/third_party/fp16/src/include -I../../deps/v8/third_party/abseil-cpp -pthread -Wno-unused-parameter -Wno-strict-overflow -Wno-return-type -Wno-int-in-bool-context -Wno-deprecated -Wno-stringop-overflow -Wno-stringop-overread -Wno-restrict -Wno-array-bounds -Wno-nonnull -Wno-dangling-pointer -flax-vector-conversions -fno-omit-frame-pointer -fdata-sections -ffunction-sections -O3 -O3 -pipe -mabi=lp64d -march=rv64gc -Werror=odr -Werror=lto-type-mismatch -Werror=strict-aliasing -Wno-template-id-cdtor -fno-tree-vectorize -fno-rtti -fno-exceptions -fno-strict-aliasing -std=gnu++20 -Wno-invalid-offsetof -c ../../deps/v8/src/compiler/backend/jump-threading.cc -o obj/deps/v8/src/compiler/backend/v8_compiler.jump-threading.o
In file included from ../../deps/v8/src/codegen/macro-assembler.h:82,
from ../../deps/v8/src/compiler/backend/code-generator-impl.h:8,
from ../../deps/v8/src/compiler/backend/jump-threading.cc:6:
../../deps/v8/src/codegen/riscv/macro-assembler-riscv.h:409:13: error: explicit specialization in non-namespace scope 'class v8::internal::MacroAssembler'
409 | template <>
| ^
../../deps/v8/src/codegen/riscv/macro-assembler-riscv.h:557:13: error: explicit specialization in non-namespace scope 'class v8::internal::MacroAssembler'
557 | template <>
| ^
There are a few instances of the error below. It looks like upstream v8 has patched some riscv issues recently.