Enable Werror with clang (#34)

Makefile.clang

@@ -5,7 +5,7 @@ CFLAGS := \
 	--target=riscv64 -march=rv64imc_zba_zbb_zbc_zbs \
 	-fPIC -O2 -fno-builtin-printf -fno-builtin-memcmp -fno-builtin-memset -nostdinc -nostdlib -fvisibility=hidden -fdata-sections -ffunction-sections \
 	-I deps/secp256k1/src -I deps/secp256k1 -I deps/ckb-c-std-lib -I deps/ckb-c-std-lib/libc -I deps/ckb-c-std-lib/molecule -I c -I build \
-	-Wall -Wno-nonnull -Wno-unused-function -g
+	-Wall -Werror -Wno-nonnull -Wno-unused-function -Wno-bitwise-instead-of-logical -g
 LDFLAGS := -nostdlib -static --gc-sections
 SECP256K1_SRC_20210801 := deps/secp256k1-20210801/src/ecmult_static_pre_context.h