qt5base-lts/mkspecs/features/device_config.prf

# Load generated qdevice.pri
DEVICE_PRI = $$[QMAKE_HOST_DATA/get]/mkspecs/qdevice.pri
exists($$DEVICE_PRI):include($$DEVICE_PRI)
unset(DEVICE_PRI)

isEmpty(CROSS_COMPILE) {
    #this variable can be persisted via qmake -set CROSS_COMPILE /foo
    CROSS_COMPILE = $$[CROSS_COMPILE]
}

# Provide a function to be used by mkspecs
defineTest(deviceSanityCheckCompiler) {
    # Check if the binary exists with an absolute path. Do this check
    # before the CROSS_COMPILE empty check below to allow the mkspec
    # to derive the compiler path from other device options.
    exists($$QMAKE_CXX):return()

    # Check for possible reasons of failure
    # check if CROSS_COMPILE device-option is set
    isEmpty(CROSS_COMPILE):error("CROSS_COMPILE needs to be set via -device-option CROSS_COMPILE=<path>")

    # Check if QMAKE_CXX points to an executable.
    system("which $$QMAKE_CXX > /dev/null"):return()

    # QMAKE_CXX does not point to a compiler.
    error("Compiler $$QMAKE_CXX not found. Check the value of CROSS_COMPILE -device-option")
}