Cross detection is too strict

[rossburton]

msetup.py:

        if env.is_cross_build():
            mlog.log('Build type:', mlog.bold('cross build'))
        else:
            mlog.log('Build type:', mlog.bold('native build'))

environment.py:

    def is_cross_build(self) -> bool:
        return not self.machines.matches_build_machine(MachineChoice.HOST)

That logic says that if the build and host machines match then we're not cross compiling, but that's incorrect. If I add some logging to is_cross_build():

| The Meson build system
| Version: 0.51.2
| Source dir: /data/poky-tmp/master/work/corei7-64-poky-linux/systemd/1_243+AUTOINC+efb536d0cb-r0/git
| Build dir: /data/poky-tmp/master/work/corei7-64-poky-linux/systemd/1_243+AUTOINC+efb536d0cb-r0/build
| is_cross_build True
| Build type: cross build
| Project name: systemd
| Project version: 243
| is_cross_build True
| C compiler for the build machine: gcc (gcc 8.3.0 "gcc (Debian 8.3.0-6) 8.3.0")
| C compiler for the host machine: x86_64-poky-linux-gcc -m64 -march=nehalem -mtune=generic -mfpmath=sse -msse4.2 -fstack-protector-strong -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Werror=format-security --sysroot=/data/poky-tmp/master/work/corei7-64-poky-linux/systemd/1_243+AUTOINC+efb536d0cb-r0/recipe-sysroot (gcc 9.2.0 "x86_64-poky-linux-gcc (GCC) 9.2.0")
| is_cross_build False

Once Meson has determined the compilers and it notices that the host machine and the build machine are both x86-64, it doesn't think we're cross building anymore.

0.50.x doesn't have this problem as it just looks for the presence of a cross file to determine whether to be cross or not. But 0.51.x doesn't do that, it simply compares the machines. #4010 by @Ericson2314 appears to be a sort of attempt to sort this out, but it's still broken.

Note that this isn't just a wrong message: once the build isn't cross anymore it stays that way, and builds will break.

[TheQwertiest]

Related(duplicate?): #5724

[rossburton]

Yes.