gcc-8-riscv64-linux-gnu produces binaries with executable stack by default

The gcc 8 RISC-V cross-compiler on Ubuntu 18.04, in contrast to other architectures such as ARM and x86, does not use noexecstack by default.

$ riscv64-linux-gnu-gcc-8 --version
'riscv64-linux-gnu-gcc-8 (Ubuntu 8.3.0-6ubuntu1~18.04.1) 8.3.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ echo "int main() { return 0; }" > test.c
$ riscv64-linux-gnu-gcc-8 test.c -o test
$ readelf -lW test|grep GNU_STACK
(no output)

Expected output:

  GNU_STACK 0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 RW 0x10

$ riscv64-linux-gnu-gcc-8 test.c -c -o test.o
$ scanelf -e test.o
 TYPE STK/REL/PTL FILE
ET_REL !WX --- --- test.o

Expected output:

 TYPE STK/REL/PTL FILE
ET_REL --- --- --- test.o

$ riscv64-linux-gnu-gcc-8 test.c -o test

I've checked with the RISC-V toolchain on Fedora, and that does set the correct GNU_STACK permissions.

So I don't think this is expected behavior, and might result in cross-compiled executables being less hardened than expected.

As a workaround, `-Wl,-z,noexecstack` can be passed to the linker, or `-Wa,-noexecstack` to gcc.