Bad order of include directories for C++ when using is_system: true

[mkow]

Describe the bug

Seems to be the same bug as #7654, but in C++ and only for directories passed with is_system: true - they end up being passed to the compiler in reversed order.

To Reproduce

project(
    'Some project name',
    'c', 'cpp',
    version: '1.0',
    meson_version: '>=0.55',
    default_options: [
        'c_std=c11',
        'cpp_std=c++14',
    ],
)
includes = [
    include_directories('/A'),
    include_directories('/B'),
    include_directories('/C', is_system: true),
    include_directories('/D', is_system: true),
    include_directories('/E', is_system: true),
]
sources = [
    'main.cpp',
]
shared_library('some-project-name',
    sources,
    include_directories: includes,
)

Compiling this project results in the following compiler invocation: (note the system includes)
ccache c++ -Ilibsome-project-name.so.p -I. -I.. -I/A -I/B -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wnon-virtual-dtor -std=c++14 -O0 -g -fPIC -isystem/E -isystem/D -isystem/C -MD -MQ libsome-project-name.so.p/main.cpp.o -MF libsome-project-name.so.p/main.cpp.o.d -o libsome-project-name.so.p/main.cpp.o -c ../main.cpp

Expected behavior

System headers should be specified in the same order as provided in include_directories.

system parameters

• plain native build (meson setup build/; meson compile -C build/)
• Ubuntu 20.04
• Python 3.8.10
• meson --version: 0.62.1
• ninja --version: 1.10.0