Enable memory overcommit

[alexgg]

Move the memory overcommit settings from the Raspberry Pi integration
layer to meta-balena so it applies to all device types.

Fixes #1791

Change-type: patch
Changelog-entry: Enable memory overcommit
Signed-off-by: Alex Gonzalez alexg@balena.io

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• Changes have been tested
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Related to https://github.com/balena-os/balena-raspberrypi/tree/alexgg/%23440-mem-overcommit

[alexgg]

Quick sanity tests:

• genericx86-64 correctly sets the vm.overcommit_memory
• Tested with values of 1 and 2, 1 correctly allows to overcommit memory (now the default) while 2 doesn't with the following snippet:

#include <stdio.h>                                                                 
#include <string.h>                                                                
#include <stdlib.h>                                                                
                                                                                   
int main (void) {                                                                  
    int n = 0;                                                                     
    char *p;                                                                       
                                                                                   
    while (1) {                                                                    
        if ((p = malloc(1<<20)) == NULL) {                                         
                printf("malloc failure after %d MiB\n", n);                        
                return 0;                                                          
        }                                                                          
        memset (p, 0, (1<<20));                                                    
        printf ("got %d MiB\n", ++n);                                              
    }                                                                              
} 

[alexgg]

Associated branch in balena-raspberrypi:
https://github.com/balena-os/balena-raspberrypi/tree/alexgg/%23440-mem-overcommit

[alexgg]

v2: Use systemd-sysctl instead

[ZubairLK]

@balena-ci retest