Makefile environment variables do not work on some host

Makefile environment variables do not work on some host

[Aymeric Dumaz]

Hello,

I have created a recipe to call multiple makefile and set a variable
if it's not defined inside them, meaning I set it before "oe_runmake".
It works as expected on a Debian testing, but with a Ubuntu base
chroot it does not.

I have written a simple recipe and the steps I used to configure the
Ubuntu chroot; on Debian I can see "var -bar-" inside log.do_compile,
but on Ubuntu it will only be "var --".
I'm not sure where the bug is located; I'm using Dunfell but I always
thought the host running Yocto was not relevant during the
compilation.
Thanks.

### Ubuntu chroot: download the image [0], extract it and start the
chroot, update it [1], add the en_US.UTF-8 locale [2], install Yocto
dependencies [3], then add an user.

### testvar.bb
SRC_URI = "file://Makefile"
LICENSE = "CLOSED"
S = "${WORKDIR}"

do_compile() {
    FOO=bar oe_runmake
}

### Makefile
all:
    @echo "var -$(FOO)-"

clean:


[0] http://cdimage.ubuntu.com/ubuntu-base/releases/20.04/release/ubuntu-base-20.04.2-base-amd64.tar.gz
[1] apt update && apt upgrade
[2] apt install locales && dpkg-reconfigure locales - select "159" then "3"
[3] apt install python3 python3-distutils binutils chrpath cpio cpp
diffstat g++ gawk gcc git make patch wget xxd