[BUG] with(out) libfs causes compilation to stop -- MISSING std_filesystem

[Wolf1098]

Describe the bug

How to reproduce

Steps to reproduce the behavior:

1. Install ce-builder:latest-aarch64 into docker
2. add swapfile and enable it, this should've been step 1, but imo doesn't change anything, at least for my machines memory usage
3. attach to docker console
4. sudo apt update && sudo apt upgrade -y
5. git clone https://github.com/CoreELEC/CoreELEC.git
6. time(PROJECT=Amlogic-CE ARCH=aarch64 DEVICE=Amlogic-ng make image

Information

• LibreELEC Version: [as included in git commit ]
• Hardware Platform: [Amlogic-ng - Odroid N2+]

Log file

UNPACK      ccache
BUILD      ccache (host)
    TOOLCHAIN      cmake-make
-- The C compiler identification is GNU 7.5.0
-- The CXX compiler identification is GNU 7.5.0
-- The ASM compiler identification is GNU
-- Found assembler: /home/docker/CoreELEC/build.CoreELEC-Amlogic-ng.arm-21/build/ccache-4.8.3/.aarch64-linux-gnu/libreelec-local-cc
-- The ASM_MASM compiler identification is unknown
-- Found assembler: ml
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /home/docker/CoreELEC/build.CoreELEC-Amlogic-ng.arm-21/build/ccache-4.8.3/.aarch64-linux-gnu/libreelec-local-cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /home/docker/CoreELEC/build.CoreELEC-Amlogic-ng.arm-21/build/ccache-4.8.3/.aarch64-linux-gnu/libreelec-local-cxx - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Ccache version: 4.8.3
-- Ccache dev mode: OFF
-- Setting CMAKE_BUILD_TYPE to Release as none was specified.
-- Performing Test std_atomic_without_libatomic
-- Performing Test std_atomic_without_libatomic - Success
-- Performing Test std_filesystem_without_libfs
-- Performing Test std_filesystem_without_libfs - Failed
-- Performing Test std_filesystem_with_libfs
-- Performing Test std_filesystem_with_libfs - Failed
CMake Error at cmake/StdFilesystem.cmake:22 (message):
  Toolchain doesn't support std::filesystem with nor without -lstdc++fs
Call Stack (most recent call first):
  cmake/StandardSettings.cmake:61 (include)
  CMakeLists.txt:72 (include)


-- Configuring incomplete, errors occurred!
FAILURE: scripts/build ccache:host during configure_host (package.mk)
*********** FAILED COMMAND ***********
cmake -DCMAKE_TOOLCHAIN_FILE=cmake-ccache.conf -DCMAKE_INSTALL_PREFIX=${TOOLCHAIN} -DENABLE_DOCUMENTATION=OFF -DREDIS_STORAGE_BACKEND=OFF -DZSTD_FROM_INTERNET=OFF -DENABLE_TESTING=OFF ..
**************************************
FAILURE: scripts/build ccache:host has failed!

Context

wasn't expecting this to work first try

[Wolf1098]

CCache needs GCC 8, installed is v7.5 by detection logs, see here for a explaination

[Wolf1098]

Hmmm, gcc8 is installed, now to investigate why gcc7.5 is being invoked, update-defaults, causing path issue, or something with cmake?

docker@ce-builder:~/CoreELEC$ grep installed ~/gcc.aptlog 
gcc/bionic-updates,bionic-security,now 4:7.4.0-1ubuntu2.3 arm64 [installed]
gcc-7/bionic-updates,bionic-security,now 7.5.0-3ubuntu1~18.04 arm64 [installed,automatic]
gcc-7-base/bionic-updates,bionic-security,now 7.5.0-3ubuntu1~18.04 arm64 [installed,automatic]
gcc-8-base/bionic-updates,bionic-security,now 8.4.0-1ubuntu1~18.04 arm64 [installed]
libcc1-0/bionic-updates,bionic-security,now 8.4.0-1ubuntu1~18.04 arm64 [installed,automatic]
libgcc-7-dev/bionic-updates,bionic-security,now 7.5.0-3ubuntu1~18.04 arm64 [installed,automatic]
libgcc1/bionic-updates,bionic-security,now 1:8.4.0-1ubuntu1~18.04 arm64 [installed]
libgomp1/bionic-updates,bionic-security,now 8.4.0-1ubuntu1~18.04 arm64 [installed,automatic]