undefined reference to `getentropy` in libstdc++

[stephanosio]

(Reported in https://discord.com/channels/720317445772017664/883404732423606303/995909013394960425)

/path/to/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.1.0/../../../../arm-zephyr-eabi/bin/ld.bfd: /path/to/opt/zephyr-sdk/arm-zephyr-eabi/arm-zephyr-eabi/lib/thumb/v7e-m/nofp/libstdc++_nano.a(random.o): in function `std::(anonymous namespace)::__libc_getentropy(void*)':
random.cc:(.text._ZNSt12_GLOBAL__N_117__libc_getentropyEPv+0x8): undefined reference to `getentropy'
/path/to/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.1.0/../../../../arm-zephyr-eabi/bin/ld.bfd: /path/to/opt/zephyr-sdk/arm-zephyr-eabi/arm-zephyr-eabi/lib/thumb/v7e-m/nofp/libstdc++_nano.a(random.o): in function `std::random_device::_M_init(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
random.cc:(.text._ZNSt13random_device7_M_initERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x3c): undefined reference to `getentropy'
/path/to/opt/zephyr-sdk/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.1.0/../../../../arm-zephyr-eabi/bin/ld.bfd: /path/to/opt/zephyr-sdk/arm-zephyr-eabi/arm-zephyr-eabi/lib/thumb/v7e-m/nofp/libc_nano.a(lib_a-arc4random.o): in function `_rs_stir_if_needed':
arc4random.c:(.text._rs_stir_if_needed+0x16): undefined reference to `getentropy'
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

Likely related upstream GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103166

Note that the "fix" for the above bug has been merged and is already part of the GCC 12.1 release, yet we still see this issue. There likely exists another underlying problem requiring further investigation.

[stephanosio]

Related GCC commit: gcc-mirror/gcc@3439657

[stephanosio]

Note that the "fix" for the above bug has been merged and is already part of the GCC 12.1 release, yet we still see this issue. There likely exists another underlying problem requiring further investigation.

This is because, in spite of gcc-mirror/gcc@60f761c adding the GCC_TRY_COMPILE_OR_LINK checks, the link check is disabled for cross compile builds.

Will fix this by disabling the automatic checks for non-native builds.