--disable-linux-apm and compile hw/xfree86/os-support/linux/lnx_apm.c

[ZssAzrael]

  CC lnx_apm.lo
hw/xfree86/os-support/linux/lnx_apm.c: In function 'xf86OSPMOpen':
hw/xfree86/os-support/linux/lnx_apm.c:153:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
cc1: some warnings being treated as errors
Makefile:660: recipe for target 'lnx_apm.lo' failed
make: *** [lnx_apm.lo] Error 1

In lnx_apm.c file:

#ifdef HAVE_ACPI
    /* Favour ACPI over APM, but only when enabled */

    if (!xf86acpiDisableFlag)
        ret = lnxACPIOpen();

    if (!ret)
#endif
#ifdef HAVE_APM
        ret = lnxAPMOpen();
#endif

I think it means

#ifdef HAVE_ACPI
    /* Favour ACPI over APM, but only when enabled */

    if (!xf86acpiDisableFlag)
        ret = lnxACPIOpen();
#endif
#ifdef HAVE_APM
    if (!ret)
        ret = lnxAPMOpen();
#endif